5 pumps working 18 hours a day can empty a tank in 12 days. How many hours a day must 6 pumps work to empty the tank in 9 days?

A19 hours

B20 hours ✓ Correct

C21 hours

D22 hours

Correct answer: (B) 20 hours

Explanation

The 6 pumps must work 20 hours a day.

Total work = 5 x 18 x 12 = 1080 pump-hours.

6 pumps for 9 days: 6 x H x 9 = 1080.

54 x H = 1080.

H = 20 hours.

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