Answer:
Given:
time taken by first pipe = 15 hours
time taken by second pipe = 5 hours
time taken by all three pipes together = 3 hours
work rates of pipes are :
1st pipe = 1/15
2nd pipe = 1/5
3rd pipe = 1/x
all together = 1/3
sum of individual rates = rate when all pipes are working together
1/15 + 1/5 + 1/x = 1/3
1/x = 1/3 - 1/15 - 1/5
solving the equation, we get
1/x = 1/ 15
x= 15
hence, it would take 15 hours for the third pipe to fill the tank.
