Advertisement

### Question

Two taps X, Y and Z can fill a tank in 18, 15 and 11 minutes respectively. All the taps are turned on at the same time. After how many minutes is the tank completely filled?

**A**

$4{146/211}$ mins.

**B**

$5{151/210}$ mins.

**C**

$3{140/213}$ mins.

**D**

$7{44/71}$ mins.

**Soln.**

**Ans: a**

Let the time be x mins. Then sum of works done by X, Y and Z = 1. $x/18 + x/15 + x/11 = 1$. Solving, we get x = $4{146/211}$. 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.