A tank has three taps. The first can fill the tank in 4 hours, the second can fill the tank in 2 hours and the third can empty the tank in 8 hours. How long will it take to fill the tank with all three taps operating at the same time? (You can assume the tank is empty to begin with).
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It will take 1 hour 36 mins to fill the tank.
In one hour the fraction, or portion, of the tank filled will be:
1/4 + 1/2 – 1/8 = 5/8
If 5/8 takes 60 mins, then 1/8 takes 12 mins, and 8/8 = 96 minutes