NCERT Solutions Class 7th Maths Chapter – 2 Fractions and Decimals All Example

Example 1. In a class of 40 students 1/5 of the total number of studetns like to study

English,2/5 of the total number like to study Mathematics and the remaining students like to study Science.

(i) How many students like to study English?
(ii) How many students like to study Mathematics?
(iii) What fraction of the total number of students like to study Science?

Solution – 

Total number of students in the class = 40.
(i) Of these 1/5 of the total number of students like to study English

Thus, the number of students who like to study English =
1/5 of 40 = 1/5 × 40 = 8.

(ii) Try yourself.

(iii) The number of students who like English and Mathematics = 8 + 16 = 24. Thus, the number of students who like Science = 40 – 24 = 16.
Thus, the required fraction is 16/40

Example 2. Sushant reads 1/3 part of a book in 1 hour. How much part of the book will he read in2 1/5 hours?

Solution – 

The part of the book read by Sushant in 1 hour = 1/3.

So, the part of the book read by him in 2 1/5 hours = 2 1/5 x 1/3
= 11/5 x 1/3 = 11×1/5×3 = 11/15

Let us now find
1/2×5/3 .We know that 5/3 = 1/3 × 5.

Example 3. The side of an equilateral triangle is 3.5 cm. Find its perimeter.

Solution – 

All the sides of an equilateral triangle are equal.
So, length of each side = 3.5 cm

Thus, perimeter = 3 × 3.5 cm = 10.5 cm

Example 4. The length of a rectangle is 7.1 cm and its breadth is 2.5 cm. What is the area of the rectangle?

Solution – 

Length of the rectangle = 7.1 cm
Breadth of the rectangle = 2.5 cm

Therefore, area of the rectangle = 7.1 × 2.5 cm2
= 17.75 cm2

Example 5. Find the average of 4.2, 3.8 and 7.6.

Solution – 

The average of 4.2, 3.8 and 7.6 is 4.2 + 3.8 + 7.6/3 =
= 5.2.

Example 6. Each side of a regular polygon is 2.5 cm in length. The perimeter of the polygon is 12.5cm. How many sides does the polygon have?

Solution – 

The perimeter of a regular polygon is the sum of the lengths of all its equal sides = 12.5 cm.

Length of each side = 2.5 cm. Thus, the number of sides = 12.5/2.5 = 12.5/2.5 = 5

The polygon has 5 sides.

Example 7. A car covers a distance of 89.1 km in 2.2 hours. What is the average distance covered by it in 1 hour?

Solution – 

Distance covered by the car = 89.1 km. Time required to cover this distance = 2.2 hours.

So distance covered by it in 1 hour = 89.1/2.2 = 89.1/2.2 =40.5km