Question

An express train is running between two stations with a uniform speed. If the diameter of each wheel of the train is $42cm$ and each wheel makes $1200$ revolutions per minute, find the speed of the train.

• A. $18km/h.$
• B. $45km/h.$
• C. $72.97km/h.$
• D. $95.04km/h.$

Answer 1

The correct option is D $95.04km/h.$

Diameter of the wheel $=42cm$
Therefore,
Radius $r=21cm$
It makes $1200$ revolution per minutes.
Distance travelled in $1$ revolution $=2\pi r$
$=\pi d$
$=\frac{22\times 42}{7}$
$=132cm$
Distance travelled in $1200$ revolution $=132\times 1200cm$
Therefore,
Speed $=\frac{132\times 1200}{1}$

$=\frac{132\times 1200\times 60km}{1\times 100\times 1000hour}$

$=95.04km/h$