how many quarts

Question

How many quarts of pure antifreeze must be added to 3 quarts of a 20​% antifreeze solution to obtain a 30​%

antifreeze​ solution?

Answer 1

x + 3*0.2 = 0.3(x+3)

x + 0.6 = 0.3x + 0.9

0.7x = 0.3

x = 3/7

3/7 of quart of pure antifreeze + 3 * 20% antifreeze =

3/7 + 0.6 qt of antifreeze =

3/7 + 6/10 = 3/7 + 3/5 = (15+21)/35 = 36/35 quarts of antifreeze

the total volume is 3 + 3/7 quarts = 24/7 quarts

36/35 divided by 24/7 = 36/35 * 7/24 = 36/(5*24) = 3/(5*2) = 3/10 = 30%

Answer: 3/7 quart of pure anti-freeze