Discussion of Question with ID = 074 under Pipes-and-Cisterns

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Two taps X, Y and Z can fill a tank in 18, 17 and 10 minutes respectively. All the taps are turned on at the same time. After how many minutes is the tank completely filled?


$4{109/164}$ mins.


$5{114/163}$ mins.


$3{103/166}$ mins.


$7{95/166}$ mins.

Ans: a

Let the time be x mins. Then sum of works done by X, Y and Z = 1. $x/18 + x/17 + x/10 = 1$. Solving, we get x = $4{109/164}$. Or use the shortcut ${abc}/{ab + bc + ca}$. Another thing, instead of solving the entire calculation, you can keep an eye on the options to find the nearest answer.

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