Question 107

Two pipes A and B can fill an empty tank in 8 hours and 12 hours respectively. They are opened alternately for 1 hour each, starting with pipe A first. In how many hours will the empty tank be filled?

Solution

let the capacity of tank = LNM (8,12)= 24L

Pipe A will fill =$$\frac{24}{8}=3L\ per\ hour$$

Pipe B will fill= $$\frac{24}{12}=2L\ per\ hour$$

If A is opened for 1 hour and then B is opened for 1 hour , they will fill 5L in 2 hours

number of such cycle = $$\frac{24}{5}=4\ or\ 5\ \ per\ hour$$

Reamaining 1 L will fill by B in 1 hour

total time taken = 4+5+1/2=$$9\frac{1}{2}$$ Ans

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