Question 76

A tank has three pipes. The first one fills up the tank in 30 min and the second one can fill it up in 45 min. The third one drains out the tank. With all the pipes open it takes 27 min to fill up the tank. Find out how long it takes the third pipe alone to empty a full tank?

Solution

1st and 2nd pipes fill the tank so addition occurs but 3rd can drain out,

$$\ \frac{\ 1}{30}+\ \frac{\ 1}{45}-\ \frac{\ 1}{x}=\ \frac{\ 1}{27}$$

by solving this we get the value of x=54

Hence option 'D' is correct.

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