Q) A works twice as fast as B. If B can complete a work in 12 days independently, the number of days in which A and B can together finish the work in :

a) 4 days              b) 6 days               c) 8 days                     d) 18 days

Ans:

Since A works twice as fast as B, then A will work twice as B or half as much time as B

If B completes the work in 12 days, A completes the work in 12/2 = 6 days

∴ A’s 1 day work = 1/6

and B’s 1 day’s work = 1/12

∴ (A + B)’s 1 day’s work = 1/6 + 1/12 = 3/12 = 1/4

Since Time taken by (A + B) to do 1/4 work = 1 day

∴ Time taken by A to do full work = 1/(1/4) = 4 days

Hence, Answer is [A].

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