A solution of 10% sulfuric acid and one of 25% sulfuric acid are to be used to make 500 ml of 20% sulfuric acid. How many ml of each solution needs to be used in the mixture? (round answers to the nearest ml)

Answer 1

amount of the 25% stuff --- x ml
amount of the 10% stuff --- 500-x ml

.25x + .1(500-x) = .2(500)

solve for x

Answer 2

25x + 1(500-x)=2(500)
25x + 500-x = 1000
25x-x = 1000-500
24x = 500
x 500/24 = 20.83