SOLUTION: An ammonia and water mixture fills a five-gallon container. Eighty percent of the mixture is ammonia but some of the mixture will be drained and replaced with pure water. I a five-

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Question 687318: An ammonia and water mixture fills a five-gallon container. Eighty percent of the mixture is ammonia but some of the mixture will be drained and replaced with pure water. I a five-gallon mixture of fifty percent ammonia is desired, how many quarts of the mixture need to be drained before the water is added? Express your answer to the nearest tenth.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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An ammonia and water mixture fills a five-gallon container.
Eighty percent of the mixture is ammonia but some of the mixture will be drained and replaced with pure water.
If a five-gallon mixture of fifty percent ammonia is desired, how many quarts of the mixture need to be drained before the water is added?
Express your answer to the nearest tenth.
:
Let x = amt to be drained (and amt to be added)
:
.80(5-x) = .50(5)
4 - .8x = 2.5
-.8x = 2.5 - 4
-.8x = -1.5
x = -1.5/-.8
x = +1.875
x ~ 1.9 gal of the original mixture drained, replaced with 1.9 gal of water