## RS Aggarwal Class 7 solutions of Chapter 7 Linear Equations in One Variable Ex 7C in pdf free download

**Objective Questions :****Mark (****✓****) against the correct answer in each of the following :****Question 1.****Solution:**

(d)

**Question 2.**

**Solution:**

(d)

**Question 3.****If (2n + 5) = 3(3n – 10), then n = ?****(a) 5****(b) 3****(c) ****(d) ****Solution:**

(a)

2n + 5 = 3 (3n – 10)

⇒ 2n + 5 = 9n – 30

⇒ 9n – 2n = 5 + 30

⇒ 7n = 35

⇒ n = 5

**Question 4.****If = , then x = ?****(a) 6****(b) 7****(c) 8****(d) 10****Solution:**

(c)

**Question 5.****If 8 (2x – 5) – 6 (3x – 7) = 1, then x = ?****(a) 2****(b) 3****(c) ****(d) ****Solution:**

(c)

8 (2x – 5) – 6 (3x – 7) = 1

⇒ 16x – 40 – 18x + 42 = 1

⇒ -2x + 2 = 1

⇒ -2x = 1 – 2 = -1

x =

**Question 6.****(a) 8****(b) 16****(c) 24****(d) 30****Solution:**

(d)

**Question 7.****Solution:**

(a)

**Question 8.****The sum of two consecutive whole numbers is 53. The smaller number is****(a) 25****(b) 26****(c) 29****(d) 23****Solution:**

(b)

Let first whole number=x

Then second number = x + 1

and sum = 53

x + x + 1 = 53

⇒ 2x = 53 – 1

⇒ 2x = 52

⇒ x = 26

Smaller number = 26

**Question 9.****The sum of two consecutive even numbers is 86. The larger of the two is****(a) 46****(b) 36****(c) 38****(d) 44****Solution:**

Let first even number = 2x

Then second number = 2x + 2

and sum = 86

2x + 2x + 2 – 86

⇒ 4x = 86 – 2 = 84

⇒ x = 21

Larger even number = 2x + 2 = 2 x 21 + 2 = 42 + 2 = 44

**Question 10.****The sum of two consecutive odd numbers is 36, the smaller one is****(a) 15****(b) 17****(c) 19****(d) 13****Solution:**

(b)

Let first odd number = 2x + 1

Second number = 2x + 3

2x + 1 + 2x + 3 = 36

⇒ 4x + 4 = 36

⇒ 4x = 36 – 4 = 32

⇒ x = 8

Smaller number = 2x + 1 = 2 x 8 + 1 = 16 + 1 = 17

**Question 11.****On adding 9 to the twice of a whole number gives 31 The whole number is****(a) 21****(b) 16****(c) 17****(d) 11****Solution:**

(d)

Let number = x

2x + 9 = 31

⇒ 2x = 31 – 9 = 22

⇒ x = 11

**Question 12.****Thrice a number when increased by 6 gives 24. The number is****(a) 6****(b) 7****(c) 8****(d) 11****Solution:**

(a)

Let number = x then

3x + 6 = 24

⇒ 3x = 24 – 6 = 18

⇒ x = 6

Number = 6

**Question 13.**** of a number is less than the original number by 10. The original number is****(a) 30****(b) 36****(c) 45****(d) 60****Solution:**

(a)

**Question 14.****Two complementary angles differ by 10°. The larger angle is****(a) 60°****(b) 50°****(c) 64°****(d) 54°****Solution:**

(b)

Let first angle = x

Then second = 90° – x

x – (90° – x) = 10

⇒ x – 90° + x = 10°

⇒ 2x = 10° + 90° = 100°

x = 50°

Second angle = 90° – 50° = 40°

Larger angle = 50°

**Question 15.****Two supplementary angles differ by 20°. The smaller of the two measures :****(a) 60°****(b) 80°****(c) 100°****(d) 120°****Solution:**

(b)

Let first angle = x

Then second = 180° – x

x – (180° – x) = 20°

⇒ x – 180° + x = 20°

⇒ 2x = 20° + 180° = 200°

x = 100°

Second angle = 180° – 100° = 80°

Smaller angle = 80°

**Question 16.****The ages of A and B are in the ratio 5 : 3. After 6 years, their ages will be in the ratio 7 : 5. The present age of A is****(a) 5 years****(b) 10 years****(c) 15 years****(d) 20 years****Solution:**

(c)

Let age of A = 5x

Then age of B = 3x

After 6 years,

A’s age = 5x + 6

and B’s age = 3x + 6

=

⇒ 25x + 30 = 21x + 42

⇒ 25x – 21x = 42 – 30

⇒ 4x = 12

⇒ x = 3

A’s age = 5x = 5 x 3 = 15 years

**Question 17.****A number when multiplied by 5 is increased by 80. The number is****(a) 15****(b) 20****(c) 25****(d) 30****Solution:**

(b)

Let the number = x

According to the condition,

5x = 80 + x

⇒ 5x – x = 80

⇒ 4x = 80

⇒ x = 20

Number = 20

**Question 18.****The length of a rectangle is three times its width and its perimeter is 96 m. The length is****(a) 12 m****(b) 24 m****(c) 36 m****(d) 48 m****Solution:**

(c)

Let width of rectangle = x m

Then length = 3x m

Perimeter = 96 m

2 (x + 3x) = 96

⇒ x + 3x = = 48

⇒ 4x = 48

⇒ x = 12

Length = 3x = 12 x 3 = 36 m

## Leave a Reply