Question

A bus has wheels which are $112cm$ in diameter. How many complete revolutions does each wheel make in $20minutes$, when the bus is travelling at a speed of $66km/h$?

Answer 1

Diameter of the wheel $=80cm$

Speed of the car $=66km/h$

Radius of the car wheel $=\frac{diameter}{2}=\frac{80}{2}=40cm.$

Distance covered by the car in one complete revolution = circumference of wheel $=2\pi r=2\ast \frac{22}{7}\ast 40cm.$

Distance covered by the car in 1 hour (60min) $=66km$

Distance covered by the car in 10minute $=\frac{66}{60}\times 10=\frac{66}{6}=11km=11km=11\ast 1000m[1km=1000m]$

$=11000m=11000\ast 100cm$

Number the revolutions made by the wheel in 10 minute

$=\frac{distancecoveredbythecarin10minutes}{distancecoveredbythecarinonecompleterevolution}=\frac{(1100000\times 7)}{(2\times 22\times 40)}=4375$

Hence,each wheel makes $4375$ Revolutions in 10 minutes.