Question

The diameter of the driving wheel of a bus is $140cm$. How many revolutions must the wheel make in a minute in order to keep a speed of $66km/hr$?

• A. 250
• B. 215
• C. 230
• D. 245

Answer 1

The correct option is A 250

1 revolution = circumference of the circle $=\pi \times d$
$=3.14\times 140$
$=439.6$ cm

Revolution in $66$ km $=\frac{6600000}{439.6}$

$=15013.6$ per hr

$=\frac{15013.6}{60}$ per min

$=\frac{15013.6}{60}$ per min

$=250.22$ per min

$\approx 250$ per min