Pipe P can fill a tank by itself

Solution

ATQ, Let the capacity of the tank = L.C.M of 16 and 36 = 144 units Then, efficiency of pipe ‘P’ alone = 144 ÷ 16 = 9 units/hour Efficiency of pipe ‘R’ alone = 144 ÷ 36 = 4 units/hour Combined efficiency of pipes ‘P’ and ‘Q’ = 144 ÷ 9 = 16 units/hour So, efficiency of pipe ‘Q’ alone = 16 – 9 = 7 units/hour So, combined efficiency of pipes ‘Q’ and ‘R’ = 7 – 4 = 3 units/hour So, time taken by pipes ‘Q’ and ‘R’ together to ill the tank = 144 ÷ 3 = 48 hours.