One tap can fill a cistern in 3 hours and the waste pipe can empty the full cistern in 5 hours.

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asked May 15 in Class VIII Maths by priya12 (-12,269 points)

One tap can fill a cistern in 3 hours and the waste pipe can empty the full cistern in 5 hours. In what time will the empty cistern be full, if the tap and the waste pipe are kept open together ?

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answered May 15 by navnit40 (-4,297 points)

One tap can fill a cistern in = 3 hours

Waste pipe can empty a cistern in = 5 hours

∴ One tap 1 hour work = 1/3

Waste pipe 1 hour work = 1/5

∴ One tap and waste pipe together 1 hour work

= 1/3 – 1/5 = (5 – 3)/15

= 2/15

∴ Empty cistern will be full in 15/2 hours

= 7. ½ hours

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