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 : Choose the correct choice from the following choices.
A) 4  B) 9  C) 12  D) 49  E) 59
Solution   Let the required number of revolutions made by larger wheel be x.   Then. More cogs, Less revolutions (Indirect Proporation)   ∴ 14: 6 :: 21 : x ⇔ 14 × x = 6 × 21 ⇔ x = (6x21/14)=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 made by the larger wheel is :