SOLUTION: a pharmacist has 700ml of a solution that is 70% active ingredient. how much pure water should she add to the solution to get a solution that is 10% active ingredient?

Question 939224: a pharmacist has 700ml of a solution that is 70% active ingredient. how much pure water should she add to the solution to get a solution that is 10% active ingredient?
Found 2 solutions by TimothyLamb, ewatrrr:
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
x = ml of pure water
y = ml of 70% ingredient/water = ml of 30% water/ingredient
z = ml of 10% ingredient/water = ml of 90% water/ingredient
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y = 700
1x + 0.30y = 0.90z
z = x + y
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put the system of linear equations into standard form
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y = 700
1x + 0.30y - 0.90z = 0
x + y - z = 0
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https://sooeet.com/math/system-of-linear-equations-solver.php
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answer:
x = ml of pure water = 4200
y = 700
z = 4900
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Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
x amount of pure water added
water = water
...
x + .30(700ml) = .90(700ml + x)
x = .60(700ml)/.10 = 4200ml, amount of pure water added

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