Ratio & Proportion

ICSE Class 6 Mathematics · Selina Solutions Concise Mathematics Class 6 ICSE · 72 solved questions

Exercise
Marks
1(i)Exercise 9(A)

Express the ratio in its simplest form :

48 : 54

Show SolutionHide Solution↓

The given ratio is 48 : 54.

H.C.F. of 48 and 54 is 6.

∴ 48 : 54 = $\frac{48 \div 6}{54 \div 6} = \frac{8}{9}$ = 8 : 9

Hence, 48 : 54 = 8 : 9.

1(ii)Exercise 9(A)

Express the ratio in its simplest form :

5 kg : 800 g

Show SolutionHide Solution↓

Both quantities must be in the same unit.

5 kg = 5 × 1000 g = 5000 g

∴ 5 kg : 800 g = 5000 g : 800 g = 5000 : 800

H.C.F. of 5000 and 800 is 200.

$\frac{5000 \div 200}{800 \div 200} = \frac{25}{4}$ = 25 : 4

Hence, 5 kg : 800 g = 25 : 4.

1(iii)Exercise 9(A)

Express the ratio in its simplest form :

3 m : 90 cm

Show SolutionHide Solution↓

Both quantities must be in the same unit.

3 m = 3 × 100 cm = 300 cm

∴ 3 m : 90 cm = 300 cm : 90 cm = 300 : 90

H.C.F. of 300 and 90 is 30.

$\frac{300 \div 30}{90 \div 30} = \frac{10}{3}$ = 10 : 3

Hence, 3 m : 90 cm = 10 : 3.

1(iv)Exercise 9(A)

Express the ratio in its simplest form :

2 years : 9 months

Show SolutionHide Solution↓

Both quantities must be in the same unit.

2 years = 2 × 12 months = 24 months

∴ 2 years : 9 months = 24 months : 9 months = 24 : 9

H.C.F. of 24 and 9 is 3.

$\frac{24 \div 3}{9 \div 3} = \frac{8}{3}$ = 8 : 3

Hence, 2 years : 9 months = 8 : 3.

1(v)Exercise 9(A)

Express the ratio in its simplest form :

$1\frac{1}{2} : 2\frac{1}{2}$

Show SolutionHide Solution↓

Converting the mixed fractions into improper fractions :

$1\frac{1}{2} : 2\frac{1}{2} = \frac{3}{2} : \frac{5}{2}$

Dividing the first term by the second term :

$= \frac{3}{2} \times \frac{2}{5} = \frac{3}{5}$ = 3 : 5

Hence, $1\frac{1}{2} : 2\frac{1}{2}$ = 3 : 5.

1(vi)Exercise 9(A)

Express the ratio in its simplest form :

$3\frac{1}{2} : 7$

Show SolutionHide Solution↓

Converting the mixed fraction into an improper fraction :

$3\frac{1}{2} : 7 = \frac{7}{2} : 7$

Dividing the first term by the second term :

$= \frac{7}{2} \times \frac{1}{7} = \frac{1}{2}$ = 1 : 2

Hence, $3\frac{1}{2} : 7$ = 1 : 2.

1(vii)Exercise 9(A)

Express the ratio in its simplest form :

2.5 : 1.5

Show SolutionHide Solution↓

Multiplying both terms by 10 to remove the decimals :

2.5 : 1.5 = 25 : 15

H.C.F. of 25 and 15 is 5.

$\frac{25 \div 5}{15 \div 5} = \frac{5}{3}$ = 5 : 3

Hence, 2.5 : 1.5 = 5 : 3.

2Exercise 9(A)

If the ratio between $x$ and $3x$ − 4 is 2 : 5, find the value of $x$.

Show SolutionHide Solution↓

Given,

$x : (3x − 4)$ = 2 : 5

$\Rightarrow \frac{x}{3x − 4} = \frac{2}{5}$

By cross multiplication :

$$\begin{aligned}\Rightarrow 5x = 2(3x - 4) \\[1em] \Rightarrow 5x = 6x - 8 \\[1em] \Rightarrow 8 = 6x - 5x \\[1em] \Rightarrow x = 8\end{aligned}$$

Hence, the value of $\bm{x = 8}$.

3Exercise 9(A)

If the ratio between $2x − 5$ and $x + 5$ is 7 : 5, find :

(i) $x$

(ii) $2x − 5$

(iii) $x + 5$

Show SolutionHide Solution↓

Given,

$(2x − 5) : (x + 5)$ = 7 : 5

$\Rightarrow \frac{2x − 5}{x + 5} = \frac{7}{5}$

By cross multiplication :

$$\begin{aligned}\Rightarrow 5(2x − 5) = 7(x + 5) \\[1em] \Rightarrow 10x − 25 = 7x + 35 \\[1em] \Rightarrow 10x − 7x = 35 + 25 \\[1em] \Rightarrow 3x = 60 \\[1em] \Rightarrow x = \frac{60}{3} = 20\end{aligned}$$

Substituting value of $x$, we get :

$2x - 5 = 2 \times 20$ - 5 = 40 - 5 = 35.

$x + 5$ = 20 + 5 = 25.

(i) Hence, $\bm{x = 20}$.

(ii) Hence, $\bm{2x - 5 = 35}$.

(iii) Hence, $\bm{x + 5 = 25}$.

4Exercise 9(A)

If $m : n$ = 4 : 3, find $3m : 4n$.

Show SolutionHide Solution↓

Solving,

$$\begin{aligned}\Rightarrow m : n = 4 : 3 \\[1em] \Rightarrow \frac{m}{n} = \frac{4}{3} \\[1em] \Rightarrow \frac{3m}{4n} = \frac{3}{4} \times \frac{4}{3} \\[1em] \Rightarrow \frac{3m}{4n} = \frac{1}{1}\end{aligned}$$

Hence, $\bm{3m : 4n = 1 : 1}$.

5Exercise 9(A)

If $p : q$ = 5 : 4, find $6p : 5q$.

Show SolutionHide Solution↓

Solving,

$$\begin{aligned}\Rightarrow p : q = 5 : 4 \\[1em] \Rightarrow \frac{p}{q} = \frac{5}{4} \\[1em] \Rightarrow \frac{6p}{5q} = \frac{6}{5} \times \frac{p}{q} \\[1em] \Rightarrow \frac{6p}{5q} = \frac{6}{5} \times \frac{5}{4} \\[1em] \Rightarrow \frac{6p}{5q} = \frac{6}{4} = \frac{3}{2}\end{aligned}$$

Hence, $\bm{6p : 5q = 3 : 2}$.

6Exercise 9(A)

A field is 80 m long and 60 m wide. Find the ratio of its width to its length.

Show SolutionHide Solution↓

Given,

Length of the field = 80 m

Width of the field = 60 m

Ratio of width to length = 60 : 80

H.C.F. of 60 and 80 is 20.

$\frac{60 \div 20}{80 \div 20} = \frac{3}{4} = 3 : 4$

Hence, the ratio of width to length is 3 : 4.

7Exercise 9(A)

Find the ratio between 5 dozens and 2 scores. [1 score = 20]

Show SolutionHide Solution↓

Given,

5 dozens = 5 × 12 = 60

2 scores = 2 × 20 = 40

Ratio = 60 : 40

H.C.F. of 60 and 40 is 20.

$\frac{60 \div 20}{40 \div 20} = \frac{3}{2} = 3 : 2$

Hence, the required ratio is 3 : 2.

8Exercise 9(A)

The monthly income of a person is ₹ 12,000 and his monthly expenditure is ₹ 8,500. Find the ratio of his :

(i) income to expenditure

(ii) expenditure to savings

(iii) savings to income

Show SolutionHide Solution↓

Given,

Monthly income = ₹ 12,000

Monthly expenditure = ₹ 8,500

Monthly savings = Income − Expenditure = ₹ 12,000 − ₹ 8,500 = ₹ 3,500

(i) Ratio of income to expenditure = 12000 : 8500

H.C.F. of 12000 and 8500 is 500.

$\frac{12000 \div 500}{8500 \div 500} = \frac{24}{17} = 24 : 17$

Hence, the ratio of income to expenditure is 24 : 17.

(ii) Ratio of expenditure to savings = 8500 : 3500

H.C.F. of 8500 and 3500 is 500.

$\frac{8500 \div 500}{3500 \div 500} = \frac{17}{7} = 17 : 7$

Hence, the ratio of expenditure to savings is 17 : 7.

(iii) Ratio of savings to income = 3500 : 12000

H.C.F. of 3500 and 12000 is 500.

$\frac{3500 \div 500}{12000 \div 500} = \frac{7}{24} = 7 : 24$

Hence, the ratio of savings to income is 7 : 24.

9Exercise 9(A)

The weekly expenses of a boy have increased from ₹ 1,500 to ₹ 2,250. Find the ratio of :

(i) increase in expenses to original expenses.

(ii) original expenses to increased expenses.

(iii) increased expenses to increase in expenses.

Show SolutionHide Solution↓

Given,

Original expenses = ₹ 1,500

Increased (new) expenses = ₹ 2,250

Increase in expenses = ₹ 2,250 − ₹ 1,500 = ₹ 750

(i) Ratio of increase in expenses to original expenses = 750 : 1500

H.C.F. of 750 and 1500 is 750.

$\frac{750 \div 750}{1500 \div 750} = \frac{1}{2} = 1 : 2$

Hence, the required ratio is 1 : 2.

(ii) Ratio of original expenses to increased expenses = 1500 : 2250

H.C.F. of 1500 and 2250 is 750.

$\frac{1500 \div 750}{2250 \div 750} = \frac{2}{3} = 2 : 3$

Hence, the required ratio is 2 : 3.

(iii) Ratio of increased expenses to increase in expenses = 2250 : 750

H.C.F. of 2250 and 750 is 750.

$\frac{2250 \div 750}{750 \div 750} = \frac{3}{1} = 3 : 1$

Hence, the required ratio is 3 : 1.

10Exercise 9(A)

In a club having 360 members, 40 play carrom, 96 play table tennis, 144 play badminton and the remaining members play volley ball. If no member plays two or more games, find the ratio of members who play :

(i) carrom to the number of those who play badminton.

(ii) badminton to the number of those who play table-tennis.

(iii) table tennis to the number of those who play volley-ball.

(iv) volley ball to the number of those who play other games.

Show SolutionHide Solution↓

Given,

Total members = 360

Carrom = 40, Table tennis = 96, Badminton = 144

Volley ball = 360 − (40 + 96 + 144) = 360 − 280 = 80

(i) Ratio of carrom to badminton = 40 : 144

H.C.F. of 40 and 144 is 8.

$\frac{40 \div 8}{144 \div 8} = \frac{5}{18} = 5 : 18$

Hence, the required ratio is 5 : 18.

(ii) Ratio of badminton to table tennis = 144 : 96

H.C.F. of 144 and 96 is 48.

$\frac{144 \div 48}{96 \div 48} = \frac{3}{2} = 3 : 2$

Hence, the required ratio is 3 : 2.

(iii) Ratio of table tennis to volley ball = 96 : 80

H.C.F. of 96 and 80 is 16.

$\frac{96 \div 16}{80 \div 16} = \frac{6}{5} = 6 : 5$

Hence, the required ratio is 6 : 5.

(iv) Members who play other games (carrom, table tennis and badminton) = 40 + 96 + 144 = 280

Ratio of volley ball to other games = 80 : 280

H.C.F. of 80 and 280 is 40.

$\frac{80 \div 40}{280 \div 40} = \frac{2}{7} = 2 : 7$

Hence, the required ratio is 2 : 7.

11Exercise 9(A)

₹ 120 is to be divided between Hari and Gopi in the ratio 5 : 3. How much does each get?

Show SolutionHide Solution↓

Given,

Total money = ₹ 120

Ratio = 5 : 3

Total parts : 5 + 3 = 8 parts.

The value of 1 part : 120 ÷ 8 = ₹ 15.

Hari's share : 5 × ₹ 15 = ₹ 75

Gopi's share : 3 × ₹ 15 = ₹ 45

Hence, Hari gets ₹ 75 and Gopi gets ₹ 45.

12Exercise 9(A)

Divide 72 in the ratio $2\frac{1}{2} : 1\frac{1}{2}$.

Show SolutionHide Solution↓

Given,

Ratio = $2\frac{1}{2} : 1\frac{1}{2} = \frac{5}{2} : \frac{3}{2}$

Multiplying both terms by 2 :

$= \frac{5}{2} \times 2 : \frac{3}{2} \times 2 = 5 : 3$

Total parts : 5 + 3 = 8 parts.

The value of 1 part : 72 ÷ 8 = 9.

First part : 5 × 9 = 45

Second part : 3 × 9 = 27

Hence, 72 is divided into 45 and 27.

13Exercise 9(A)

Divide ₹ 10,400 among A, B and C in the ratio $\frac{1}{2} : \frac{1}{3} : \frac{1}{4}$.

Show SolutionHide Solution↓

Given ratio = $\frac{1}{2} : \frac{1}{3} : \frac{1}{4}$

L.C.M. of the denominators 2, 3 and 4 is 12.

Multiplying each term by 12 :

$\frac{1}{2} \times 12 : \frac{1}{3} \times 12 : \frac{1}{4} \times 12 = 6 : 4 : 3$

Let the shares of A, B and C be 6x, 4x and 3x respectively.

⇒ 6x + 4x + 3x = 10400

⇒ 13x = 10400

⇒ x = $\frac{10400}{13}$

⇒ x = ₹ 800

Shares are :

A's share = 6x = 6 × ₹ 800 = ₹ 4,800,

B's share = 4x = 4 × ₹ 800 = ₹ 3,200,

C's share = 3x = 3 × ₹ 800 = ₹ 2,400.

Hence, A gets ₹ 4,800, B gets ₹ 3,200 and C gets ₹ 2,400.

14Exercise 9(A)

The angles of a triangle are in the ratio 3 : 7 : 8. Find the greatest and the smallest angles.

Show SolutionHide Solution↓

Given,

Ratio of the angles = 3 : 7 : 8

Let the angles be 3x, 7x and 8x.

The sum of the angles of a triangle = 180°

⇒ 3x + 7x + 8x = 180°

⇒ 18x = 180°

⇒ x = $\frac{180^{\circ}}{18}$

⇒ x = 10°

Angles are :

3x = 3 × 10° = 30°,

7x = 7 × 10° = 70°,

8x = 8 × 10° = 80°.

Hence, the greatest angle is 80° and the smallest angle is 30°.

15Exercise 9(A)

The sides of a triangle are in the ratio 3 : 2 : 4. If the perimeter of the triangle is 27 cm, find the length of each side.

Show SolutionHide Solution↓

Given,

Ratio of the sides = 3 : 2 : 4

Perimeter of the triangle = 27 cm

Let the sides be 3x, 2x and 4x.

⇒ 3x + 2x + 4x = 27

⇒ 9x = 27

⇒ x = $\frac{27}{9}$

⇒ x = 3 cm

Sides are :

3x = 3 × 3 cm = 9 cm,

2x = 2 × 3 cm = 6 cm,

4x = 4 × 3 cm = 12 cm.

Hence, the lengths of the sides are 9 cm, 6 cm and 12 cm.

1Exercise 9(B)

In each of the following, check whether or not the given ratios form a proportion :

(i) 8 : 16 and 12 : 15

(ii) 16 : 28 and 24 : 42

(iii) 98 : 112 and 14 : 16

Show SolutionHide Solution↓

(i) 8 : 16 and 12 : 15

Simplifying first ratio :

$\Rightarrow \frac{8}{16} = \frac{1}{2}$

Simplifying second ratio :

$\Rightarrow \frac{12}{15} = \frac{4}{5}$

∴ Ratio 8 : 16 ≠ 12 : 15.

Hence, 8 : 16 and 12 : 15 do not form a proportion.

(ii) 16 : 28 and 24 : 42

Simplifying first ratio :

$\Rightarrow \frac{16}{28} = \frac{4}{7}$

Simplifying second ratio :

$\Rightarrow \frac{24}{42} = \frac{4}{7}$

∴ Ratio 16 : 28 = 24 : 42.

Hence, 16 : 28 and 24 : 42 form a proportion.

(iii) 98 : 112 and 14 : 16

Simplifying first ratio :

$\Rightarrow \frac{98}{112} = \frac{7}{8}$

Simplifying second ratio :

$\Rightarrow \frac{14}{16} = \frac{7}{8}$

∴ Ratio 98 : 112 = 14 : 16.

Hence, 98 : 112 and 14 : 16 form a proportion.

2(i)Exercise 9(B)

Find the value of x so that the given four numbers are in proportion :

x, 6, 10 and 15

Show SolutionHide Solution↓

Four numbers a, b, c, d are in proportion if a × d = b × c.

x, 6, 10 and 15

⇒ x × 15 = 6 × 10

⇒ 15x = 60

⇒ x = $\frac{60}{15}$ = 4

Hence, x = 4.

2(ii)Exercise 9(B)

Find the value of x so that the given four numbers are in proportion :

2, x, 10 and 25

Show SolutionHide Solution↓

Four numbers a, b, c, d are in proportion if a × d = b × c.

2, x, 10 and 25

⇒ 2 × 25 = x × 10

⇒ 50 = 10x

⇒ x = $\frac{50}{10}$ = 5

Hence, x = 5.

2(iii)Exercise 9(B)

Find the value of x so that the given four numbers are in proportion :

9, 12, x and 8

Show SolutionHide Solution↓

Four numbers a, b, c, d are in proportion if a × d = b × c.

9, 12, x and 8

⇒ 9 × 8 = 12 × x

⇒ 72 = 12x

⇒ x = $\frac{72}{12}$ = 6

Hence, x = 6.

2(iv)Exercise 9(B)

Find the value of x so that the given four numbers are in proportion :

6, 4, 18 and x

Show SolutionHide Solution↓

Four numbers a, b, c, d are in proportion if a × d = b × c.

6, 4, 18 and x

⇒ 6 × x = 4 × 18

⇒ 6x = 72

⇒ x = $\frac{72}{6}$ = 12

Hence, x = 12.

3(i)Exercise 9(B)

Find the value of x in the following proportion :

(x + 5) : 24 = 3 : 4

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

(x + 5) : 24 = 3 : 4

⇒ 4(x + 5) = 24 × 3

⇒ 4(x + 5) = 72

⇒ x + 5 = $\frac{72}{4}$

⇒ x + 5 = 18

⇒ x = 18 − 5 = 13

Hence, x = 13.

3(ii)Exercise 9(B)

Find the value of x in the following proportion :

14 : (x − 1) = 7 : 9

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

14 : (x − 1) = 7 : 9

⇒ 14 × 9 = 7(x − 1)

⇒ 126 = 7(x − 1)

⇒ x − 1 = $\frac{126}{7}$

⇒ x − 1 = 18

⇒ x = 18 + 1 = 19

Hence, x = 19.

3(iii)Exercise 9(B)

Find the value of x in the following proportion :

2 : 3 = (x − 2) : 18

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

2 : 3 = (x − 2) : 18

⇒ 2 × 18 = 3(x − 2)

⇒ 36 = 3(x − 2)

⇒ x − 2 = $\frac{36}{3}$

⇒ x − 2 = 12

⇒ x = 12 + 2 = 14

Hence, x = 14.

3(iv)Exercise 9(B)

Find the value of x in the following proportion :

3 : 4 = 30 : (x + 10)

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

3 : 4 = 30 : (x + 10)

⇒ 3(x + 10) = 4 × 30

⇒ 3(x + 10) = 120

⇒ x + 10 = $\frac{120}{3}$

⇒ x + 10 = 40

⇒ x = 40 − 10 = 30

Hence, x = 30.

3(v)Exercise 9(B)

Find the value of x in the following proportion :

1 : 2 = (x − 1) : 26

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

1 : 2 = (x − 1) : 26

⇒ 1 × 26 = 2(x − 1)

⇒ 26 = 2(x − 1)

⇒ x − 1 = $\frac{26}{2}$

⇒ x − 1 = 13

⇒ x = 13 + 1 = 14

Hence, x = 14.

4Exercise 9(B)

The first, second and the fourth terms of a proportion are 6, 18 and 75 respectively. Find its third term.

Show SolutionHide Solution↓

Let the third term be x.

∴ 6, 18, x and 75 are in proportion, i.e. 6 : 18 : : x : 75

In a proportion, product of extremes = product of means.

⇒ 6 × 75 = 18 × x

⇒ 450 = 18x

⇒ x = $\frac{450}{18}$ = 25

Hence, the third term is 25.

5Exercise 9(B)

The ratio of copper and zinc in an alloy by weight is 9 : 8. If the weight of zinc in the alloy is 9.6 kg, find the weight of copper in the alloy.

Show SolutionHide Solution↓

Given,

Ratio (Copper : Zinc) = 9 : 8

Weight of zinc = 9.6 kg

Since 8 parts represent the zinc, 8 parts = 9.6 kg.

1 part = $\frac{9.6}{8}$ = 1.2 kg.

Weight of copper = 9 parts = 9 × 1.2 = 10.8 kg.

Hence, the weight of copper in the alloy is 10.8 kg.

6Exercise 9(B)

The ratio of the number of girls to the number of boys in a school is 2 : 5. If the number of boys is 225, find :

(i) the number of girls in the school.

(ii) the number of total students in the school.

Show SolutionHide Solution↓

Given,

Ratio (Girls : Boys) = 2 : 5

Number of boys = 225

Since 5 parts represent the boys, 5 parts = 225.

1 part = $\frac{225}{5}$ = 45.

(i) Number of girls = 2 parts = 2 × 45 = 90.

Hence, the number of girls in the school is 90.

(ii) Total students = Girls + Boys = 90 + 225 = 315.

Hence, the total number of students in the school is 315.

7Exercise 9(B)

If $(3x − 4) : (x + 2)$ = 2 : 1, find the value of $x$.

Show SolutionHide Solution↓

Given,

$(3x - 4) : (x + 2)$ = 2 : 1

⇒ $\frac{3x - 4}{x + 2} = \frac{2}{1}$

By cross multiplication :

$$\begin{aligned}\Rightarrow 3x − 4 = 2(x + 2) \\[1em] \Rightarrow 3x − 4 = 2x + 4 \\[1em] \Rightarrow 3x − 2x = 4 + 4 \\[1em] \Rightarrow x = 8\end{aligned}$$

Hence, the value of $\bm{x = 8}$.

8Exercise 9(B)

If (x − 7) : 2 : : (x − 3) : 3, find the value of x − 5.

Show SolutionHide Solution↓

Given,

(x − 7) : 2 : : (x − 3) : 3

In a proportion, product of extremes = product of means.

⇒ 3(x − 7) = 2(x − 3)

⇒ 3x − 21 = 2x − 6

⇒ 3x − 2x = 21 − 6

⇒ x = 15

Now, x − 5 = 15 − 5 = 10

Hence, the value of x − 5 is 10.

9Exercise 9(B)

In a school three out of every 5 students play cricket. If there are 2,400 students in the school, find how many of them play cricket?

Show SolutionHide Solution↓

Given,

Out of every 5 students, 3 play cricket.

∴ Fraction of students who play cricket = $\frac{3}{5}$

Number of students who play cricket = $\frac{3}{5} \times 2400$

= 3 × 480

= 1440.

Hence, 1440 students play cricket.

1Exercise 9(C)

The price of 25 identical articles is ₹ 1,750. Find the price of 13 articles.

Show SolutionHide Solution↓

Given,

Price of 25 articles = ₹ 1,750

Price of 1 article = $\frac{1750}{25}$ = ₹ 70.

Price of 13 articles = 13 × ₹ 70 = ₹ 910.

Hence, the price of 13 articles is ₹ 910.

2Exercise 9(C)

A motorbike travels 330 km consuming 5 litres of petrol. How much distance will it cover consuming 2.5 litres of petrol?

Show SolutionHide Solution↓

Given,

Distance covered in 5 litres = 330 km

Distance covered in 1 litre = $\frac{330}{5}$ = 66 km.

Distance covered in 2.5 litres = 2.5 × 66 = 165 km.

Hence, the motorbike will cover 165 km consuming 2.5 litres of petrol.

3Exercise 9(C)

The cost of 35 envelopes is ₹ 105. How many envelopes can be bought for ₹ 90?

Show SolutionHide Solution↓

Given,

Cost of 35 envelopes = ₹ 105

Number of envelopes bought for ₹ 105 = 35

Number of envelopes bought for ₹ 1 = $\frac{35}{105}$ envelopes.

Number of envelopes bought for ₹ 90 = $\frac{35}{105} \times 90$

= $\frac{1}{3} \times 90$

= 30 envelopes.

Hence, 30 envelopes can be bought for ₹ 90.

4Exercise 9(C)

The cost of 10 kg of wheat is ₹ 180;

(i) what will 18 kg of wheat cost?

(ii) what quantity of wheat can be purchased for ₹ 432?

Show SolutionHide Solution↓

Given,

Cost of 10 kg of wheat = ₹ 180

Cost of 1 kg of wheat = $\frac{180}{10}$ = ₹ 18.

(i) Cost of 18 kg of wheat = 18 × ₹ 18 = ₹ 324.

Hence, 18 kg of wheat costs ₹ 324.

(ii) Quantity of wheat purchased for ₹ 18 = 1 kg

Quantity of wheat purchased for ₹ 432 = $\frac{432}{18}$ = 24 kg.

Hence, 24 kg of wheat can be purchased for ₹ 432.

5Exercise 9(C)

A tree 24 m high casts a shadow of 15 m. At the same time, another tree casts a shadow of 6 m. Find the height of the second tree.

Show SolutionHide Solution↓

Given,

Height of the first tree = 24 m, shadow of the first tree = 15 m

Shadow of the second tree = 6 m

For a shadow of 15 m, the height = 24 m

For a shadow of 1 m, the height = $\frac{24}{15}$ m.

For a shadow of 6 m, the height = $\frac{24}{15} \times 6$

= $\frac{144}{15}$

= 9.6 m

Hence, the height of the second tree is 9.6 m.

6Exercise 9(C)

A loaded truck travels 18 km in 25 minutes. If the speed remains the same, how far will it travel in 2 hours?

Show SolutionHide Solution↓

Given,

Distance travelled in 25 minutes = 18 km

2 hours = 2 × 60 minutes = 120 minutes

Distance travelled in 1 minute = $\frac{18}{25}$ km.

Distance travelled in 120 minutes = $\frac{18}{25} \times 120$

= $\frac{2160}{25}$

= 86.4 km.

Hence, the truck will travel 86.4 km in 2 hours.

7Exercise 9(C)

Jai Singh and Vijay Singh start a business by investing ₹ 6,00,000 and ₹ 9,00,000 respectively. At the end of the year, they earn a profit of ₹ 1,50,000. What is the share of Vijay Singh out of this profit?

Show SolutionHide Solution↓

Given,

Jai Singh's investment = ₹ 6,00,000

Vijay Singh's investment = ₹ 9,00,000

Total profit = ₹ 1,50,000

Ratio of investments = 600000 : 900000 = 6 : 9 = 2 : 3

Let the shares of Jai Singh and Vijay Singh be 2x and 3x respectively.

⇒ 2x + 3x = 150000

⇒ 5x = 150000

⇒ x = $\frac{150000}{5}$

⇒ x = ₹ 30,000

Vijay Singh's share = 3x = 3 × ₹ 30,000 = ₹ 90,000.

Hence, the share of Vijay Singh is ₹ 90,000.

8Exercise 9(C)

Out of 350 students, 150 are girls. Find the ratio of :

(i) number of girls to the total number of students.

(ii) number of boys to the number of girls.

Show SolutionHide Solution↓

Given,

Total students = 350

Number of girls = 150

Number of boys = 350 − 150 = 200

(i) Ratio of girls to total students = 150 : 350

H.C.F. of 150 and 350 is 50.

$\frac{150 \div 50}{350 \div 50} = \frac{3}{7} = 3 : 7$

Hence, the ratio of girls to the total number of students is 3 : 7.

(ii) Ratio of boys to girls = 200 : 150

H.C.F. of 200 and 150 is 50.

$\frac{200 \div 50}{150 \div 50} = \frac{4}{3} = 4 : 3$

Hence, the ratio of boys to girls is 4 : 3.

9Exercise 9(C)

If the cost of one dozen identical articles is ₹ 166. What is the cost of 36 such articles?

Show SolutionHide Solution↓

Given,

Cost of one dozen (12) articles = ₹ 166

36 articles = 3 dozens

Cost of 36 articles = 3 × ₹ 166 = ₹ 498.

Hence, the cost of 36 articles is ₹ 498.

10Exercise 9(C)

A car moves with a uniform speed and covers 180 km in 3 hours.

(i) In how much time will it cover 240 km?

(ii) How much distance will it cover in 2 hours?

Show SolutionHide Solution↓

Given,

Distance covered in 3 hours = 180 km

Speed of the car = $\frac{180}{3}$ = 60 km/h.

(i) Time taken to cover 240 km = $\frac{240}{60}$ = 4 hours.

Hence, the car will cover 240 km in 4 hours.

(ii) Distance covered in 2 hours = 60 × 2 = 120 km.

Hence, the car will cover 120 km in 2 hours.

1Test Yourself

Is the ratio of 15 kg and 35 kg same as the ratio of 6 years and 14 years?

Show SolutionHide Solution↓

Ratio of 15 kg and 35 kg = 15 : 35

H.C.F. of 15 and 35 is 5.

$\frac{15 \div 5}{35 \div 5} = \frac{3}{7} = 3 : 7$

Ratio of 6 years and 14 years = 6 : 14

H.C.F. of 6 and 14 is 2.

$\frac{6 \div 2}{14 \div 2} = \frac{3}{7} = 3 : 7$

Since both ratios are equal to 3 : 7, they are the same.

Hence, yes, the two ratios are the same.

2Test Yourself

A bus travels 180 km in 3 hours and a train travels 450 km in 5 hours. Find the ratio of the speed of train to the speed of bus.

Show SolutionHide Solution↓

Given,

Speed of bus = $\frac{180}{3}$ = 60 km/h

Speed of train = $\frac{450}{5}$ = 90 km/h

Ratio of speed of train to speed of bus = 90 : 60

H.C.F. of 90 and 60 is 30.

$\frac{90 \div 30}{60 \div 30} = \frac{3}{2} = 3 : 2$

Hence, the ratio of the speed of the train to the speed of the bus is 3 : 2.

3Test Yourself

In winters, a school opens at 10 a.m. and closes at 3.30 p.m. If the lunch interval is of 30 minutes, find the ratio of lunch interval to total time of the class periods.

Show SolutionHide Solution↓

Given,

School opens at 10 a.m. and closes at 3.30 p.m.

Total time the school is open = 5 hours 30 minutes = 5 × 60 + 30 = 330 minutes

Lunch interval = 30 minutes

Total time of the class periods = 330 − 30 = 300 minutes

Ratio of lunch interval to total time of the class periods = 30 : 300

H.C.F. of 30 and 300 is 30.

$\frac{30 \div 30}{300 \div 30} = \frac{1}{10} = 1 : 10$

Hence, the ratio of lunch interval to total time of the class periods is 1 : 10.

4Test Yourself

Rohit goes to his school by car at 60 km per hour and Manoj goes to the same school by scooty at 40 km per hour. If they both live in the same locality, find the ratio between the time taken by Rohit and Manoj to reach their school.

Show SolutionHide Solution↓

Given,

Speed of Rohit = 60 km/h

Speed of Manoj = 40 km/h

Since both cover the same distance, time is inversely proportional to speed.

∴ Ratio of time taken by Rohit to Manoj = $\frac{1}{60} : \frac{1}{40}$

Multiplying both terms by the L.C.M. of 60 and 40, i.e. 120 :

$= \frac{1}{60} \times 120 : \frac{1}{40} \times 120 = 2 : 3$

Hence, the ratio between the time taken by Rohit and Manoj is 2 : 3.

5Test Yourself

An alloy of zinc and copper weighs $12\frac{1}{2}$ kg. If, in the alloy, the ratio of zinc and copper is 1 : 4, find the weight of copper in it.

Show SolutionHide Solution↓

Given,

Total weight of the alloy = $12\frac{1}{2}$ kg = $\frac{25}{2}$ kg = 12.5 kg

Ratio (Zinc : Copper) = 1 : 4

Let the weights of zinc and copper be x and 4x respectively.

⇒ x + 4x = 12.5

⇒ 5x = 12.5

⇒ x = $\frac{12.5}{5}$

⇒ x = 2.5 kg

Weight of copper = 4x = 4 × 2.5 = 10 kg.

Hence, the weight of copper in the alloy is 10 kg.

6Test Yourself

Find the fourth term of the proportion whose first, second and third terms are 18, 27 and 32 respectively.

Show SolutionHide Solution↓

Let the fourth term be x.

∴ 18, 27, 32 and x are in proportion, i.e. 18 : 27 : : 32 : x

In a proportion, product of extremes = product of means.

⇒ 18 × x = 27 × 32

⇒ 18x = 864

⇒ x = $\frac{864}{18}$ = 48

Hence, the fourth term is 48.

7Test Yourself

The ratio of the length and the width of a school ground is 5 : 2. Find the length, if the width is 40 metres.

Show SolutionHide Solution↓

Given,

Ratio (Length : Width) = 5 : 2

Width = 40 m

Since 2 parts represent the width, 2 parts = 40 m.

1 part = $\frac{40}{2}$ = 20 m.

Length = 5 parts = 5 × 20 = 100 m.

Hence, the length of the school ground is 100 m.

8Test Yourself

Two numbers are in the ratio 9 : 2. If the smaller number is 320, find the larger number.

Show SolutionHide Solution↓

Given,

Ratio of the two numbers = 9 : 2

The smaller number corresponds to 2 parts.

Since 2 parts represent the smaller number, 2 parts = 320.

1 part = $\frac{320}{2}$ = 160.

Larger number = 9 parts = 9 × 160 = 1440.

Hence, the larger number is 1440.

9Test Yourself

Ratio of the distance of the school from A's house and from B's house is 2 : 1. If both A and B have the same speed, complete the following table :

Distance (in km) from A's house to schoolDistance (in km) from B's house to the same school
4_
_9
8_
_8
6_
Show SolutionHide Solution↓

Given,

Ratio of the distance of the school from A's house to that from B's house = 2 : 1.

∴ Distance from A's house = 2 × (Distance from B's house), and Distance from B's house = $\frac{1}{2}$ × (Distance from A's house).

Completing each column using this relation :

When distance from A's house = 4 km, distance from B's house = $\frac{1}{2} \times 4 = 2$ km.

When distance from B's house = 9 km, distance from A's house = 2 × 9 = 18 km.

When distance from A's house = 8 km, distance from B's house = $\frac{1}{2} \times 8 = 4$ km.

When distance from B's house = 8 km, distance from A's house = 2 × 8 = 16 km.

When distance from A's house = 6 km, distance from B's house = $\frac{1}{2} \times 6 = 3$ km.

The completed table is :

Distance (in km) from A's house to schoolDistance (in km) from B's house to the same school
42
189
84
168
63
10Test Yourself

Mr. Gupta divides ₹ 81,000 among his three children, Ashok, Mohit and Geeta, in such a way that Ashok gets four times what Mohit gets and Mohit gets 2.5 times what Geeta gets. Find the share of each of them.

Show SolutionHide Solution↓

Given,

Total money = ₹ 81,000

Let Geeta's share = 1 part.

Mohit gets 2.5 times what Geeta gets, so Mohit's share = 2.5 parts.

Ashok gets four times what Mohit gets, so Ashok's share = 4 × 2.5 = 10 parts.

∴ Ratio (Ashok : Mohit : Geeta) = 10 : 2.5 : 1

Multiplying each term by 2 to remove the decimal :

= 20 : 5 : 2

Let the shares of Ashok, Mohit and Geeta be 20x, 5x and 2x respectively.

⇒ 20x + 5x + 2x = 81000

⇒ 27x = 81000

⇒ x = $\frac{81000}{27}$

⇒ x = ₹ 3,000

Shares are :

Ashok's share = 20x = 20 × ₹ 3,000 = ₹ 60,000,

Mohit's share = 5x = 5 × ₹ 3,000 = ₹ 15,000,

Geeta's share = 2x = 2 × ₹ 3,000 = ₹ 6,000.

Hence, Ashok gets ₹ 60,000, Mohit gets ₹ 15,000 and Geeta gets ₹ 6,000.

11Test Yourself

If $(4x + 3y) : (3x + 5y)$ = 6 : 7, find :

(i) $x : y$

(ii) $x$, if $y$ = 10

(iii) $y$, if $x$ = 27

Show SolutionHide Solution↓

(i) Given,

$(4x + 3y) : (3x + 5y)$ = 6 : 7

⇒ $\frac{4x + 3y}{3x + 5y} = \frac{6}{7}$

By cross multiplication :

$$\begin{aligned}\Rightarrow 7(4x + 3y) = 6(3x + 5y) \\[1em] \Rightarrow 28x + 21y = 18x + 30y \\[1em] \Rightarrow 28x − 18x = 30y − 21y \\[1em] \Rightarrow 10x = 9y \\[1em] \Rightarrow \frac{x}{y} = \frac{9}{10}\end{aligned}$$

Hence, $\bm{x : y = 9 : 10}$.

(ii) Since, $\frac{x}{y} = \frac{9}{10}$, we have $x = \frac{9}{10} y$.

$x = \frac{9}{10} \times 10$ = 9

Hence, $\bm{x = 9}$ when $\bm{y = 10}$.

(iii) Since, $\frac{x}{y} = \frac{9}{10}$, we have $y = \frac{10}{9} x$.

$y = \frac{10}{9} \times 27$ = 10 × 3 = 30

Hence, $\bm{y = 30}$ when $\bm{x = 27}$.

12Test Yourself

If $\frac{2y + 5x}{3y − 5x} = 2\frac{1}{2}$, find :

(i) $x : y$

(ii) $x$, if $y$ = 70

(iii) $y$, if $x$ = 33

Show SolutionHide Solution↓

(i) Given,

$\frac{2y + 5x}{3y − 5x} = 2\frac{1}{2} = \frac{5}{2}$

By cross multiplication :

$$\begin{aligned}\Rightarrow 2(2y + 5x) = 5(3y − 5x) \\[1em] \Rightarrow 4y + 10x = 15y − 25x \\[1em] \Rightarrow 10x + 25x = 15y − 4y \\[1em] \Rightarrow 35x = 11y \\[1em] \Rightarrow \frac{x}{y} = \frac{11}{35}\end{aligned}$$

Hence, $\bm{x : y = 11 : 35}$.

(ii) Since, $\frac{x}{y} = \frac{11}{35}$, we have $x = \frac{11}{35} y$.

$x = \frac{11}{35} \times 70$ = 11 × 2 = 22

Hence, $\bm{x = 22}$ when $\bm{y = 70}$.

(iii) Since, $\frac{x}{y} = \frac{11}{35}$, we have $y = \frac{35}{11} x$.

$y = \frac{35}{11} \times 33$ = 35 × 3 = 105

Hence, $\bm{y = 105}$ when $\bm{x = 33}$.

11 Mark · Multiple Choice Questions

Ratio of 350 m to 1 km is :

Show SolutionHide Solution↓

Both quantities must be in the same unit.

1 km = 1000 m

Ratio = 350 : 1000

H.C.F. of 350 and 1000 is 50.

$\frac{350 \div 50}{1000 \div 50} = \frac{7}{20} = 7 : 20$

Hence, option 2 is the correct option.

21 Mark · Multiple Choice Questions

Simple ratio of $\frac{7}{3} : 3 : \frac{5}{4}$ is :

Show SolutionHide Solution↓

Given ratio = $\frac{7}{3} : 3 : \frac{5}{4}$

L.C.M. of the denominators 3, 1 and 4 is 12.

Multiplying each term by 12 :

$\frac{7}{3} \times 12 : 3 \times 12 : \frac{5}{4} \times 12 = 28 : 36 : 15$

Hence, option 3 is the correct option.

31 Mark · Multiple Choice Questions

Natural numbers p, q, r and s are in proportion, if :

Show SolutionHide Solution↓

If p, q, r and s are in proportion, i.e. p : q : : r : s, then

product of extremes = product of means

⇒ p × s = q × r

Hence, option 3 is the correct option.

41 Mark · Multiple Choice Questions

In a proportion, the two extreme terms are 18 and 15. If one of the two means is 30, the other mean term is :

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

Product of extremes = 18 × 15 = 270

Let the other mean term be x.

⇒ 30 × x = 270

⇒ x = $\frac{270}{30}$ = 9.

Hence, option 1 is the correct option.

51 Mark · Multiple Choice Questions

The angles of a triangle are in the ratio 3 : 7 : 8. The sum of its smallest and the largest angle is :

Show SolutionHide Solution↓

The sum of the angles of a triangle = 180°

Let the angles be 3x, 7x and 8x.

⇒ 3x + 7x + 8x = 180°

⇒ 18x = 180°

⇒ x = $\frac{180^{\circ}}{18}$

⇒ x = 10°

The angles are 3 × 10° = 30°, 7 × 10° = 70° and 8 × 10° = 80°.

Smallest angle = 30° and largest angle = 80°.

Sum of the smallest and the largest angle = 30° + 80° = 110°.

Hence, option 3 is the correct option.

61 Mark · Multiple Choice Questions

If 5 : 7 : : 9 : x, the value of x is :

Show SolutionHide Solution↓

In a proportion, product of extremes = product of means.

⇒ 5 × x = 7 × 9

⇒ 5x = 63

⇒ x = $\frac{63}{5}$ = 12.6

Hence, option 1 is the correct option.

71 Mark · Multiple Choice Questions

Two numbers are in the ratio 7 : 5 and the sum of these numbers is 126. The larger number is :

Show SolutionHide Solution↓

Ratio of the two numbers = 7 : 5

Let the two numbers be 7x and 5x.

⇒ 7x + 5x = 126

⇒ 12x = 126

⇒ x = $\frac{126}{12}$

The larger number = 7x = 7 × $\frac{126}{12} = \frac{126}{12} × 7$.

Hence, option 4 is the correct option.

81 Mark · Multiple Choice Questions

The ratio of zinc and copper in an alloy is 3 : 7. If the weight of copper in the alloy is 70 g, the weight of zinc in it is :

Show SolutionHide Solution↓

Ratio (Zinc : Copper) = 3 : 7

Since 7 parts represent the copper, 7 parts = 70 g.

1 part = $\frac{70}{7}$ = 10 g.

Weight of zinc = 3 parts = 3 × 10 = 30 g.

Hence, option 1 is the correct option.

91 Mark · Multiple Choice Questions

Cost of 20 identical articles is ₹ 600. Then the cost of 30 such articles is :

Show SolutionHide Solution↓

Cost of 20 articles = ₹ 600

Cost of 1 article = $\frac{600}{20}$ = ₹ 30.

Cost of 30 articles = 30 × ₹ 30 = ₹ 900.

Hence, option 2 is the correct option.

101 Mark · Multiple Choice Questions

Ratios 40 cm to 2 m and ₹ 30 to ₹ 150 form a proportion.

Show SolutionHide Solution↓

First ratio : 40 cm to 2 m

2 m = 200 cm

40 : 200 = $\frac{40}{200} = \frac{1}{5}$ = 1 : 5

Second ratio : ₹ 30 to ₹ 150

30 : 150 = $\frac{30}{150} = \frac{1}{5}$ = 1 : 5

Since both ratios are equal to 1 : 5, they form a proportion.

Hence, option 1 is the correct option.

11Statement I-II Type Questions

Statement 1 : Two numbers $A$ and $B$ are in the ratio 3 : 5, then $A = \frac{3}{5} × B$.

Statement 2 : $\frac{A}{3} = \frac{B}{5}$

Which of the following options is correct?

Show SolutionHide Solution↓

Given,

$A$ and $B$ are in the ratio 3 : 5.

∴ $\frac{A}{B} = \frac{3}{5}$

$\Rightarrow A = \frac{3}{5} × B$.

So, Statement 1 is true.

From $A : B$ = 3 : 5, we get $\frac{A}{B} = \frac{3}{5}$, which on cross multiplication gives $5A = 3B$, i.e. $\frac{A}{3} = \frac{B}{5}$.

So, Statement 2 is true.

Hence, option 1 is the correct option.

12Statement I-II Type Questions

Statement 1 : If $m : n$ = 5 : 4, then $5m : 4n$ = 25 : 16

Statement 2 : $5m : 4n = \frac{5m}{4n} = \frac{5}{4} \times \frac{5}{4} = 25 : 16$

Show SolutionHide Solution↓

Given,

$m : n$ = 5 : 4, i.e. $\frac{m}{n} = \frac{5}{4}$.

Solving,

$$\begin{aligned}\Rightarrow 5m : 4n = \frac{5m}{4n} \\[1em] = \frac{5}{4} \times \frac{m}{n} \\[1em] = \frac{5}{4} \times \frac{5}{4} \\[1em] = \frac{25}{16} \\[1em] = 25 : 16\end{aligned}$$

So, Statement 2 is true.

From the working above, $5m : 4n$ = 25 : 16.

So, Statement 1 is true.

Hence, option 1 is the correct option.

13Assertion Reason Type Questions

Assertion (A) : A car covers a distance of 140 km in 2 hours. The average speed of car = 70 km/h.

Reason (R) : For the same distance, if the speed is more, then the time taken is less.

Show SolutionHide Solution↓

We know that,

Average speed = $\frac{\text{Distance}}{\text{Time}} = \frac{140}{2} = 70$ km/h.

So, Assertion (A) is true.

For a fixed distance, speed and time are inversely proportional, so the greater the speed, the less the time taken.

So, Reason (R) is true.

Hence, option 3 is the correct option.

Press ↓ to reveal a solution and move to the next question. Back to Selina Solutions Concise Mathematics Class 6 ICSE.