Question

6 pipes are required to fill a tank in 1 hour 20 minutes. How long will it take if only 5 pipes of the same type are used?

Answer 1

Let the desired time to fill the tank be x minutes. Thus, we have the following table.

Number of pipes	6	5
Time (in minutes)	80	x

Lesser the number of pipes more will be the time required by it to fill the tank. So, this is a case of inverse proportion.

Hence, 80 × 6 = x × 5.......[x₁y₁ = x₂y₂]

`(80 xx 6)/5 = x`

x = 96

Thus, time taken to fill the tank by 5 pipes is 96 minutes or 1 hour 36 minutes.