rnaah wrote:Pumps A, B, and C are used to fill a particular pool. Working together, pumps A and B can fill the pool in 6/5 hrs, A and C in 3/2 hrs and B and C in 2 hrs. Working together, how many hours will all three machines take to fill the pool?
Let the pool = 18 units.
Rate for A+B = w/t = 18/(6/5) = 15 units per hour.
Rate for A+C = w/t = 18/(3/2) = 12 units per hour.
Rate for B+C = w/t = 18/2 = 9 units per hour.
Combining the rates:
(A+B) + (A+C) + (B+C) = 15+12+9 = 36.
2A + 2B + 2C = 36.
A+B+C = 18 units per hour.
Time for A+B+C to fill the pool = w/r = 18/18 = 1 hour.
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