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.
 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