Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternately, the tank will be full in_________?
Q1. Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternately, the tank will be full in_________?
Answer: 7 hours
Explanation: In every 2-hour cycle, A fills 2/12, B fills 1/15, C fills 1/20; combined per 2 hrs = 1/6+1/15+1/20 = 19/60; after 6 hrs (3 cycles) 19/20 is filled, leaving 1/20 which A fills in 1/5 hr; total ≈ 7 hours.