Answer:
24.83 hours
Step-by-step explanation:
Given that :
Let time taken by pumps be :
Pump A = 60 hours
Pump B = 80 hours
Pump C = 90 hours
Recall :
Rate = 1 / time taken
The rates of the pumps are :
Pump A rate = 1 / 60
Pump B rate = 1/80
Pump C rate = 1/90
Combined rate : 1/60 + 1/80 + 1/90
Combined rate = (12 + 9 + 8) / 720 = 29/720
Combined rate = 29/720
The time taken together will be :
1 / combined rate = 1/(29/720) = 720 / 29 = 24.827 hours
