SOLUTION: the hot water faucet fills a tub in 40 min and the cold faucet fills it in 30 min. The tub can be drained in 20 min. If both faucets are turned on and the drain is open, how soon w

Question 423289: the hot water faucet fills a tub in 40 min and the cold faucet fills it in 30 min. The tub can be drained in 20 min. If both faucets are turned on and the drain is open, how soon will and empty tub be filled?
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
in 10 min, the hot faucet fills 1/4 (10/40) of the tub; the cold faucet fills 1/3 (10/30) of the tub;
and the drain empties 1/2 (10/20) of the tub

1/4 + 1/3 - 1/2 = 3/12 + 4/12 - 6/12 = 1/12

if it takes 10 min to fill 1/12 of the tub; it takes 120 min (12 * 10) or 2 hr to fill the whole tub
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