SOLUTION: Achemist has 600ml of a solution that is half acid. She needs a solution that is 70% acid. How many mL of acid she should add?

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Question 295139: Achemist has 600ml of a solution that is half acid. She needs a solution that is 70% acid. How many mL of acid she should add?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A chemist has 600ml of a solution that is half acid.
He needs a solution that is 70% acid.
How many mL of acid he should add?
:
Let x = amt of acid required
:
A typical mixture equation
:
.50(600) + x = .70(x+600)
300 + x = .70x + 420
x - .7x = 420 - 300
.3x = 120
x = 120%2F.3
x = 400 ml
:
:
Check
.5(600) + 400 = .7(400 + 600)
300 + 400 = .7(1000)