Three pumps, each working 8 hours per day, can empty a tank in 2 days. How many hours per day must four pumps work to empty the tank in 1 day?

Given data

• 3 pumps × 8 h/day × 2 days empty the tank
• Find hours/day for 4 pumps to finish in 1 day

Concept / Approach

• Total work (emptying the tank) is proportional to the total pump-hours.
• So, (number of pumps) × (hours per day) × (days) = constant for the same tank.

Step-by-step calculation

Total pump-hours needed = 3 × 8 × 2 = 48 pump-hoursLet required hours/day for 4 pumps be H. Then 4 × H × 1 = 48H = 48 ÷ 4 = 12 hours/day

Verification

4 pumps × 12 h = 48 pump-hours, same as original requirement.

Common pitfalls

• Adding or averaging times; this is a direct work (rate × time) problem.

Final Answer

12 hours/day