Filling a TubDate: 6/11/96 at 17:58:49 From: Michael Balazs Subject: Word Problem - Filling a Tub Faucet A will fill a tub in 45 minutes. Faucet B will fill the same tub in 20 minutes. How long will it take to fill the tub if both faucets are opened at the same time? For this problem I don't even know where to start. Date: 6/11/96 at 18:48:08 From: Dr. Anthony Subject: Re: Word Problem - Filling a Tub Think of the proportion of the tub that is filled PER MINUTE by each faucet. For A it is 1/45 of the full tub, while for B it is 1/20 of the full tub per minute. So in 1 minute, with A and B together it is 1/45 + 1/20 = 13/180 of the tub. So if t=time, then (13/180)t = 1 t = 180/13 = 13.846 minutes t = 13 +11/13 minutes -Doctor Anthony, The Math Forum Date: Wed, 12 Jun 1996 14:59:23 -0400 From: Michael Balazs Subject: Re: Word Problem - Filling a Tub Thank you. What about this one? A faucet takes 20 minutes to fill an empty tub. The drain takes 50 minutes to empty the tub when it is full. If both the faucet and the drain are opened at the same time, how long will it take to fill the empty tub? Michael Balazs Date: Fri, 14 Jun 1996 12:17:40 -0400 (EDT) From: Dr. Anthony Subject: Re: Word Problem - Filling a Tub You use the same ides as before. The proportion of the tank filled per minute by inlet pipe is 1/20, while the proportion emptied per minute is 1/50. When operating together the proportion being filled is 1/20 - 1/50 = 3/100. If t = time to fill the tank under these conditions, then t(3/100) = 1 t = 100/3 = 33 +1/3 minutes. -Doctor Anthony, The Math Forum |
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