Together, the three intake pipes, "P," "Q," and "R," can

Solution

ATQ, Let quantity filled by pipe ‘P’, ‘Q’ and ‘R’ together in 8 hrs = 1 litres Quantity filled by pipe ‘P’, ‘Q’ and ‘R’ together in 1 hrs = (1/8) litres Quantity filled by pipe ‘P’, ‘Q’ and ‘R’ together in 3 hrs = (3/8) litres Remaining quantity to be filled = {1 – (3/8)} = (5/8) litres Quantity filled by pipe ‘P’ and ‘R’ together in 9 hrs = (5/8) litres Quantity filled by pipe ‘P’ and ‘R’ together in 1 hrs = (5/72) litres Quantity filled by pipe ‘Q’ alone in 1 hour = (1/8) – (5/72) = (4/72) litres So, pipe ‘Q’ alone can fill the tank in (72/4) = 18 hrs