Eight identical pumps operating independently can empty a tank in 9 hours. How many hours would 12 such pumps take to empty the same tank? Enter the number of hours.
Bonne réponse
6
Explication
Emptying the tank takes 8 times 9, or 72 pump-hours, so 12 pumps take 72 divided by 12, which is 6 hours. Scaling 9 hours upward to 13.5 hours treats the relationship as direct and predicts that more pumps take longer.