Two pipes A and B can fill a tank in 50hour and 75 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank? Select.
A) 15hrs
B) 20hrs
C) 25hrs
D) 30hrs
E) 32hrs
Part filled by A in 1 hour = 1/50   part filled by B in 1 hour = 1/75   Part filled by A+B in 1 hour = 1/50 + 1/75 = 1/30   Both the pipes will together will fill the tank in 30 hours.   Answer is 30hrs
<result>D</result>
Two pipes A and B can fill a tank in 50hour and 75 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?