How many liters of pure acid should be added to 9 liters of 45% concentrate to raise the concentration to 70%?

Answer 1

.45(9) + x = .7(9+x)

4.05 + x = 6.3 +.7x

x-.7x = 6.3-4.05

.3x = 2.25

x = 2.25/.3 = 7.5 Liters of pure acid

check the answer

.45(9) +7.5 = 6.3 +7.5(.7)

4.05 +7.5 =6.3 + 5.25

11.55 = 11.55

.1-.7 = .3

.7-.45 = .25

30/25 = 6/5 = 1.2

1.2 times as much 45% is needed as 100%

1.2 = 9/x

x =9/1.2 = 7.5 Liters of pure acid