Pipe 'A' can fill a tank in 24 hours, while Pipe 'B' takes 36 hours to fill the same tank. If Pipe 'B' is opened first and Pipe 'A' is turned on after a delay of ___ hours, ______ hours will it take to completely fill the tank from the time Pipe 'A' starts flowing? The values given in which of the following options will fill the blanks in the same order in which is it given to make the statement true?
I. 8, 11.2
II. 11, 10
III. 15, 8.4

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.