Let the time taken by pipe C to empty the tank be t minutes. Suppose the capacity of the tank be V units Therefore, amount of tank filled by pipe A in 50 minutes + Amount of tank filled by pipe B in 50 minutes – Amount of tank emptied by pipe Cin 50 minutes = V
⇒
V
60
×50+
V
75
×50−
V
t
×50=V
⇒
50
t
=
5
6
+
2
3
−1=
1
2
⇒ t = 100 minutes Thus, pipe C will empty the tank in 100 minutes