SOLUTION: I have a quiz tomorrow and this is a problem on my homework, I could really use some help! A chemist has a 60% acid solution and a 20% acid solution. How many millimeters of eac

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Question 1004755: I have a quiz tomorrow and this is a problem on my homework, I could really use some help!
A chemist has a 60% acid solution and a 20% acid solution. How many millimeters of each should be used to make 140ml of a 35% acid solution? Let x represent the number of ml of the 60% acid solution.
Thanks so much!!
Found 2 solutions by josgarithmetic, stanbon:
Answer by josgarithmetic(39617) (Show Source):
You can put this solution on YOUR website!
This is how the method can work:
Using just a single variable to solve a two-part mixture problem - example

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
A chemist has a 60% acid solution and a 20% acid solution. How many millimeters of each should be used to make 140ml of a 35% acid solution? Let x represent the number of ml of the 60% acid solution.
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Using two equations::
Quantity:: s + t = 140 ml
Acid Eq:::0.60s + 0.20t = 0.35*140
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Modify for elimination:
60s + 60t = 60*140
60s + 20t = 35*140
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Subtract and solve for "t"::
40t = 25*140
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t = 87.5 ml (amt. of 20% solution needed
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s = 140-t = 52.5 ml (amt. of 60% solution needed)
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OR
Using one equation:
acid + acid = acid
0.60x + 0.20(140-x) = 0.35*140
Multiply thru by 100 to get:
60x + 20*140 - 20x = 35*140
40x = 15*140
x = 52.5 ml (amt. of 60% solution needed)
140-x = 87.5 ml (amt. of 20% solution needed)
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Cheers,
Stan H.
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