Two pipes A & B can fill a tank in 15 minutes & 20 minutes respectively. Both the pipes are opened together but after 4 minutes , pipe A is turned off. What is the total time required to fill the tank
সমাধান
সঠিক উত্তর: Option C
Part filled in 4 mins = 4(1/15 + 1/20) = 7/15
Remaining part = 1 - 7/15 = 8/15
Part Filled by B in 1 min 1/20
So,
1/20 : 8/15 = 1: x
x = 10 min 40 sec
total time 14 min 40 sec
