Answer with Explanation:

Let the required number of working hours per day be x.

More pumps, Less working hours per day (Indirect Proportion)

Less days, More working hours per day (Indirect Proportion)

Pumps 4:3 }
                   :: 8 : x
Days 1:2     }

Therefore, 4 x 1 x x = 3 x 2 x 8

=> x =(3 x 2 x 8)/ (4)

=> x = 12.

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