Pipe 'A' can fill a tank in 24 hours, while Pipe 'B'

Solution

Let the capacity of the tank be 72 litres. So, efficiency of pipe 'A' = (72/24) = 3 litres/hour And efficiency of pipe 'B' = (72/36) = 2 litres/hour For I: Tank filled by pipe 'B' in 8 hours = 2 X 8 = 16 litres And remaining capacity of the tank = 72 ­ - 16 = 56 litres So, time taken by both pipes to fill the tank = 56 ÷ (3 + 2) = 11.2 hours So, statement I is true. For II: Tank filled by pipe 'B' in 11 hours = 2 X 11 = 22 litres And remaining capacity of the tank = 72 ­ - 22 = 50 litres So, time taken by both pipes to fill the tank = 50 ÷ (3 + 2) = 10 hours So, statement II is true. For II: Tank filled by pipe 'B' in 15 hours = 2 X 15 = 30 litres And remaining capacity of the tank = 72 ­ - 30 = 42 litres So, time taken by both pipes to fill the tank = 42 ÷ (3 + 2) = 8.4 hours So, statement III is true.