Discussion of Question with ID = 016 under Pipes-and-Cisterns

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Question

A tank is filled in 4 minutes by three taps running together. Tap A is twice as fast as tap B, and tap B is twice as fast as tap C. How much time will tap A take to fill the tank?

A

28 mins.

B

29 mins.

C

27 mins.

D

30 mins.

Soln.
Ans: a

Let the time taken by tap A be x mins. Then 4 minutes work of all the taps should add to 1. So we have, $4 × 1/x + 4 × 2/x + 4 × 4/x$ = 1, which is same as $4 × 7/x$ = 1. Solving, we get x = 28 mins.

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