The wheel of a motorcycle 70cm in diameter makes 40 revolutions in every 10sec.What is the speed of motorcycle n km/hr?

A 13.68kmph

B 31.68kmph

C 41.68kmph

D 45.68kmph

Correct Answer: Option B

In this type of question, we will first calculate the distance covered in given time.

Distance covered will be : Number of revolutions x Circumference

So we will be having distance and time, from which we can calculate the speed.

Radius of wheel = 70 / 2 = 35 cm

Distance covered in 40 revolutions will be

\(40\ast circumferene=40\ast2\mathrm{πr}=40\ast2\ast\frac{22}7\ast35=8800\mathrm{cm}\)

= 88 m

Distance covered in 1 sec = \(\frac{88}{10}=8.8m/s=8.8\ast\frac{18}5km/hr=31.68km/hr\)