Question

A cistern has a leak which would empty it in 8 hours.A tap is turned on which admits 6 litres a minute in the cistern, and it is now emptied in 12 hours. How many litres does the cistern hold?

• A. 8460 L
• B. 4320 L
• C. 8640 L
• D. 4230 L

Answer 1

Answer:

C. 8640 L

Work done by leak in 1 hour = 1/8 Total work done by both pipes in 1 hour = 1/12 Work done by the pipe in 1 h = (1 / 8 – 1 / 12) = 1 / 24 Work done by the pipe in 1 min = 1 / 24 × 1 / 60 = 1 / 1440 Volume of 1 / 1440 part = 6L Volume of the whole cistern = 6 × 1440 = 8640