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### Question

Two taps X, Y and Z can fill a tank in 4, 16 and 6 minutes respectively. All the taps are turned on at the same time. After how many minutes is the tank completely filled?

**A**

$2{2/23}$ mins.

**B**

$3{5/22}$ mins.

**C**

1 mins.

**D**

$4{17/25}$ mins.

**Soln.**

**Ans: a**

Let the time be x mins. Then sum of works done by X, Y and Z = 1. $x/4 + x/16 + x/6 = 1$. Solving, we get x = $2{2/23}$. 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.