Bunuel wrote:
Two hoses (A and B) are filling a pool. Working alone at their individual constant rates Hose A could fill the pool in 6 hours, and Hose B could do it in 4 hours. If Hose A works alone for one hour and then Hose B joins after that, how long will it take in total for the pool to be filled?
A. 2 hours
B. 2 hours, 12 minutes
C. 2 hours, 48 minutes
D. 3 hours
E. 3 hours, 12 minutes
Let the capacity of the Pool be 12 units
So, Efficiency of Hose A is 2 units/hour & Efficiency of Hose B is 3 units/hour
Work completed by A in 1 hour is 2 units, so 10 Units of work is left
Combined efficiency of A & B is 5 units/hour.
So, The time taken to fill 10 units is 10/5 = 2 Hours
Thus, the total time taken to fill the Pool will be 1 + 2 = 3 Hours, Answer must be (D)
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