James wants to make a 5% alcohol solution. He has already poured 3 qt of pure water into a beaker.How many qt of a 20% alcohol solution must he add to this to create the desired mixture?

Answer 1

Let T = the number of quarts needed of twenty percent solution to make 5% solution

T+3 = the total number of quarts of 5% solution

20(T) = 5(T+3)

20T = 5T + 15

15T = 15

T = 1 quart

1 quart of 20% + 3 quarts of 0% = 4 quarts of 5%

the 20% is spread throughout 4 quarts, with 20/4 = 5% as the result

each quart of 5% solution will have 3/4 water and 1/4 of 20% solution mixed together