Question

A large rubber cushion can be filed with air pump in 10 minutes, another pump can fill the same cushion in 12 minutes. if both the pumps operate together, how long wil take to fill the cushion? a)6 5/11minutes b)5 6/11 minutes c)4 5/11minutes d)5 5/11 minutes.

Answer 1

X 1/10

Y 1/12

X+Y 6+5/60

60/11 MINS

=

5 5/11 MINS

Answer 2

Given,

Two Air pumps of different capacities.

One air pump can fill a large rubber cushion in 10 mins.

Another air pump can fill the large rubber cushion in 12 mins.

To Find,

In how much time the large cushion be filled if both the pumps are operated together.

Solution,

The first air pump can fill $\frac{1}{10}^{th}$ part of the cushion in 1 min.

The second air pump can fill $\frac{1}{12} ^{th}$ part of the cushion in 1 min.

Thus if both the air pumps operate together, then $\frac{1}{10}$  + $\frac{1}{12}$ $= \frac{11}{60}$ part of the cushion one 1 min.

Thus both the pumps together can fill the pump in $\frac{60}{11}$ mins.

Henceforth, both the pumps together can fill the cushion in $5\frac{5}{11}$ mins, thus option "d" is the answer.