Question

9 pumps of equal capacity can empty a tank in 36 min. How long will it tank to empty the tank if 5 pumps out of these were switched off ?​

Answer 1

9 pumps take time 36min

1 pumps take time 36÷9 = 4

So, 5 pumps take time 5 × 4 = 20min

Answer 2

This is the solution of your Question and if you have a doubt that how does this 4 came than in the question it is written that 5 pumps out of these were switched off so, 9-5 =4