Q1:
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:
A 49
B 9
C 4
D 12
ANS:B - 9
Let the required number of revolutions made by larger wheel be x.
Then, More cogs, Less revolutions (Indirect Proportion) 14 : 6 :: 21 : x 14 x x = 6 x 21
14 : 6 :: 21 : 
14 x 