Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
The diameter of the driving wheel of a bus is 140 cm. How many revolutions per minute must the wheel make in order to keep a speed of 66 km per hour?
(a)200
(b)250
(c)300
(d)350
Answer
Answer (as printed): B
Explanation
Distance covered in 1 revolution $$=\left(2 \times \frac{22}{7} \times 70\right) \mathrm{cm}=440 \mathrm{cm} .$$ Number of revolutions made in 1 hr $$=\left(\frac{66 \times 1000 \times 100}{440}\right)=15000 . \therefore \quad \text { Number of revolutions per minute }=\frac{15000}{60}=250 .$$