Two pipes can fill a cistern separately in 36 minutes and 45 minutes, respectively. A waste pipe can drain off 40 litres per minute. If all the three pipes are opened, the cistern fills in one hour. The capacity (in litres of the cistern) is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 1200.
Given:
Two pipes can fill a cistern separately in 36 minutes and 45 minutes, respectively
Explanation:
Let the capacity be C units
The rate of first pipe = C/36 units/minute
The rate of second pipe = C/45 units/minute
A waste pipe can drain off 40 litres per minute
According to the question
⇒ C/36 + C/45 - 40 = C/60
⇒ (5C + 4C - 3C) = 180 × 40
⇒ 6C = 180 × 40
⇒ C = 1200