# RD Sharma Solutions Class 7 Mathematics Solutions for Mensuration 2 Exercise 21.1 in Chapter 21 - Mensuration 2 Area of Circle

Question 16 Mensuration 2 Exercise 21.1

A boy is cycling such that the wheels of the cycle are making 140 revolutions per minute. If the diameter of the wheel is 60 cm, calculate the speed per hour with which the boy is cycling.

Given the diameter of the wheel = 60 cm

Distance covered by the wheel in 1 revolution = Circumference of the wheel

Distance covered by the wheel in 1 revolution = π d

= 22/7 × 60 cm

Distance covered by the wheel in 140 revolutions = 22/7 × 60 × 140

= 26400 cm

Thus, the wheel covers 26400 cm in 1 minute. Then,

Speed = 26400/100 × 60 m/hr

= 264 × 60 m/hr

= 264 × 60/1000 km/hr

= 15.84 km/hr

The speed with which the boy is cycling is 15.84 km/hr.

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"hello students welcome to lido q a video session i am sef your science tutor and question for today is when is the body said to be at rest a body is referred to be in the state of rest or stationary when there is no change in its position so when the body doesn't change its position with respect to its immediate surrounding we can say that it is at the rest so this can be written as a body is referred to be in state of rest when it doesn't changes its position with respect to its immediate surroundings so this is our answer if you have any queries you can drop it in comment section and subscribe to lino for more q a thank you for watching"
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