7 pumps working 10 hours a day empty a tank in 20 days. How many hours a day must 5 pumps work to empty a similar tank in 14 days?

A20 hours ✓ Correct

B18 hours

C16 hours

D14 hours

Correct answer: (A) 20 hours

Explanation

Each pump must work 20 hours a day.

The total work in pump-hours is fixed.

7 x 10 x 20 = 1400 pump-hours.

Set 5 x H x 14 = 1400.

70 H = 1400, so H = 20.

This applies pumps x hours x days = constant.

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