Question
A tank of capacity 60 litres can be filled in 10 minutes by a pipe P. Another pipe Q placed at the bottom of tank can empty the tank in 30 minutes. Both of the pipes were opened. In how much time pipe Q will empty the tank if pipe P is closed after 10 minutes?
CAT 2021
Solution
Correct option is (C)
(C)
Explanatory Answer :
part of tank filled in 1 minute by pipe P = 60/10 = 6 litres
part of tank emptied in 1 minute by pipe Q = 60/30 = 2 litres
part of tank filled by pipe P and Q together in 1 minute= 6 - 2 = 4 litres
part of tank filled by pipe P and Q together in 10 minutes =10*4 = 40 litres
time taken by Q to empty 40 litres = 40/2 = 20 minutes
20 is the correct answer