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 sixty percent ammonia is desired, how many quarts of the mixture need to be drained before the water is added? (A quart is onefourth of a gallon.)
+128475 4 galllons of the current mixture is ammonia (80% of 5)
We need 3 gallons of ammonia at the end
Let x be the number of gallons drained off and.8x the amount of ammonia drained off
(4 - .8x) = .6 *5
4 - .8x = 3
4 - 3 = .8x
1 = .8x
1/.8 = x = 1.25
We need to drian off 1.25 gal
Proof
4 gallons of ammmonia to start with
When we drain away 1.25 gallons, 80% of this is ammonia.....so 4 - .8(1.25) = 3 gallons of ammonia are left
Adding back 1.25 gallons of pure water = 5 gallons and 3 of this is ammonia...so....3/5= .60 = 60%
And 1.25 gallons = 5 qts
