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## Practice Test Discussion

Q)

A cistern can be filledup in 14 hours by an inlet M. Another outlet N can empty the cistern in 18 hours. If both the inlets M and N are opened together, then after how long will the cistern be fully filled?

• Explanation

According to the formula, if pipe A can comletely fils a tank in x hours and pipe B can comletely empty the tank in y hours, then the time taken by both pipes together to fill the tank is $\frac{\mathrm{xy}}{\mathrm{x}-\mathrm{y}}$ hours.

So,

The tank will be filled by both the pipe opened simultaneously in 63 hours

Hence option B is correct

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