⟩ Suppose Pipe A can fill in 20 minutes and Pipe B in 30 mins and Pipe C can empty the same in 40 mins. If all of them work together, find the timetaken to fill the tank?
a fill - 1/20 per minute
b fill - 1/30 per minute
c can empty - 1/40 per minute
Suppose this take x minute
1 x +1x - 1x
--- -- ---- =1
20 30 40
Solve this x=17(approximately)