Question

Ten pipes of the same type can fill up a tank in $16$ minutes. If two pipes go out of order, how long will the remaining pipes take to fill the tank ?

• A. $18$ mins
• B. $20$ mins
• C. $22$ mins
• D. $24$ mins

Answer 1

The correct option is B $20$ mins

If $x$ is the required number of hour then,
In order to solve this problem, first, we need to find out whether the proportionality is direct or inverse.
Now, here we note that:
For more number of pipes, the time required to fill is less.
For less number of pipes, the time required to fill is more.
Hence, there is an inverse proportionality.
$10\times 16=(10-2)\times x$
where, x is the time required.
$\Rightarrow 10\times 16=8\times x$
$\Rightarrow x=\frac{10\times 16}{8}$
$=10\times 2$
$=20$ mins.