Subject: General Aptitude · Chapter: Area · Exam: 2007 · Marks: · Difficulty:
A toothed wheel of diameter 50 cm is attached to a smaller wheel of diameter 30 cm. How many revolutions will the smaller wheel make when the larger one makes 15 revolutions?
(a)18
(b)20
(c)25
(d)30
Answer
Answer (as printed): C
Explanation
Distance covered by smaller wheel in 1 revolution $$=(2 \pi \times 15) \mathrm{cm}=(30 \pi) \mathrm{cm} .$$ Distance covered by larger wheel in 1 revolution $$=(2 \pi \times 25) \mathrm{cm}=(50 \pi) \mathrm{cm} .$$ Let $k \times 30 \pi=15 \times 50 \pi$. Then, $k=\left(\frac{15 \times 50 \pi}{30 \pi}\right)=25$. $$\therefore \quad \text { Required number of revolutions }=25 .$$
Explanation as extracted from the printed page; notation may be imperfect.