When Blanca puts the stopper in place and the faucet running, the bathtub can be filled in 16 minuets. When she turns the faucet off and removes, the tub will empty in 20 minuets. If Blanca turns the faucet on and does not put the stopper in place, how long will it take her to fill the tub?

It needs an equation to find the answer

Please

Guest Apr 27, 2015

#3**+10 **

Since the bathtub can be filled in 16 minutes, the rate is 1 bathtub / 16 minutes or 1/16.

Since the bathtub can be emptied in 20 minutes, the rate is -1 bathtub / 20 minutes or -1/20.

Let n be the number of minutes. The point is to get 1 full bathtub = 1.

Filling + Emptying = 1 Bathtub

(1/16)n - (1/20)n = 1

Multiply each term by 320:

320(1/16)n - 320(1/20)n = 320(1)

20n - 16n = 320

4n = 320

---> n = 80 minutes

geno3141
Apr 27, 2015

#3**+10 **

Best Answer

Since the bathtub can be filled in 16 minutes, the rate is 1 bathtub / 16 minutes or 1/16.

Since the bathtub can be emptied in 20 minutes, the rate is -1 bathtub / 20 minutes or -1/20.

Let n be the number of minutes. The point is to get 1 full bathtub = 1.

Filling + Emptying = 1 Bathtub

(1/16)n - (1/20)n = 1

Multiply each term by 320:

320(1/16)n - 320(1/20)n = 320(1)

20n - 16n = 320

4n = 320

---> n = 80 minutes

geno3141
Apr 27, 2015