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_________?

A. Rs. 150
B. Rs. 144
C. Rs. 138
D. Rs. 132
E. None of these
Explanation:
Given that SP = Rs. 102 and loss = 15%
CP = [100(SP)]/(100 – l%) = (100 * 102)/85 = 20 * 6 = Rs. 120.
To get 20% profit, New SP = [(100 + p%)CP]/100 = (120 * 120)/100 = Rs. 144