Determine the time taken by a pipe R to empty a water tank. Statement I: Pipe P and pipe Q can fill a water tank in 6 hours and 8 hours, respectively. If all pipes P, Q, and R are opened together, the time taken by all three pipes to fill the water tank is 120/23 hours. Statement II: Pipe P can fill the water tank in 6 hours, and the ratio of the efficiencies of pipes Q and R is 2:1.

ATQ, Statement I: Let, the total capacity of tank be 120 units. Efficiency of P = 120/6 = 20 units/hr Efficiency of Q = 120/8 = 15 units/hr Let, the efficiency of R be 'a' units/hr. So, 120/23 = 120/(20 + 15 – a) Or, 120/23 = 120/(35 – a) Or, a = 12 Time taken by pipe R to empty the water tank = 120/12 = 10 hours So, data in statement I alone is sufficient to answer the question. Statement I: We cannot determine the relation between pipes P, Q and R. So, data in statement II alone is not sufficient to answer the question.