Two pipes fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 min. The capacity of the tank is?
Solution
Correct Answer: Option C
Work done by the waste pipe in 1 min
\(= \frac{1}{{15}} - \left( {\frac{1}{20} + \frac{1}{{24}}} \right) = \left( {\frac{1}{{15}} - \frac{{11}}{{120}}} \right) \Rightarrow \frac{{ - 1}}{{40}}\)
\(\Rightarrow {\rm{}}\frac{{ - 1}}{{40}}{\rm{}}\) (-ve sign means emptying)
∴ Volume of \(\frac{1}{{40}}\) part = 3 gallons
Volume of tank
⇒ (3×40) gallons
⇒ 120 gallons
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