A wheel that has 6 cogs is meshed with a larger wheel of 14 cogs. When the smaller wheel has made 21… · ABC26GN3332
Subject: General Aptitude · Chapter: Chain Rule
A wheel that has 6 cogs is meshed with a larger wheel of 14 cogs. When the smaller wheel has made 21 revolutions, then the number of revolutions made by the larger wheel is
(a)4
(b)9
(c)12
(d)49
Answer
Answer (as printed): B
Explanation
Let the required number of revolutions made by larger wheel be $x$. Then, More cogs, Less revolutions (Indirect Proportion) $$\begin{array}{ll} \therefore & 14: 6:: 21: x \\ \Leftrightarrow & 14 \times x=6 \times 21 \Leftrightarrow x=\left(\frac{6 \times 21}{14}\right)=9 . \end{array}$$
Explanation as extracted from the printed page; notation may be imperfect.