Two taps A and B can fill an overhead tank in 10 hours and 15 hours respectively. Both the taps are opened for 4 hours and then B is turned off. How much time will A take to fill the remaining tank?
Given,
Tap A can fill a tank in= 10 hours
Tap B can fill the tank in = 15 hours
Work done by Tap A in 1 hour = 
Work done by tap B in 1 hour = 
∴ Work done by both tap in 1 hour = 
Work done by both tap in 4 hours = 
Remaining part = 
Hence, time taken by A to fill remaining part = 
hours
25