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:
Choose the correct answer:
A) 4  B) 9  C) 12  D) 49  E) 40
Explanation: Let the required number of revolutions made by larger wheel be x.   Then, More cogs, Less revolutions (Indirect Proportion)   14 : 6 :: 21 : x &lt;-&gt; 14 x x = 6 x 21   x = (6 x 21)/14   x = 9   Answer 9
<result>B</result>
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: