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 mad by the larger wheel is:
4
9
12
49
Explanation:
Let the required number of revolutions made by larger wheel be $ x $.
Then, More cogs, Less revolutions (Indirect Proportion)
$\therefore$ 14 : 6 :: 21 : $ x $ $\Leftrightarrow$ 14 x $ x $ = 6 x 21
| $\Rightarrow x $ =$ \dfrac{6 \times 21}{14} $ |
$\Rightarrow x $ = 9.