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  1. 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:
    1. 4
    2. 9
    3. 14
    4. 7
Correct Option: B

Suppose that required number of revolutions made by larger wheel be N.
Then, More cogs, Less revolutions (Indirect Proportion)
We can write as -
14 : 6 :: 21 : N ⇔ 14 x N = 6 x 21

⇒ N = 6 x 21
14

⇒ N = 3 x 3 = 9 revolutions .
Hence required answer is 9 revolutions .



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