The radius of a wheel is 70 cm. If the wheel makes 10 revolutions in 5 seconds covering a certain distance, then the speed of the wheel is:

Correct option is D

Given:

Radius of the wheel = 70 cm

The wheel makes 10 revolutions in 5 seconds

​Formula Used:

Circumference of circle =$$2\pi r$$​​
Speed $$= \frac{\text{Distance}}{\text{Time}}$$

Solution:

Total Distance covered = 10 × Circumference of wheel

Total Distance covered $$= 10 \times 2 \times \frac{22}{7} \times \frac{70}{100} = 44 \text{ meters}$$​​

Speed = ​$$\frac{44}{5} \times \frac{18}{5} = 31.68 \ \text{km/h}$$​