SOLUTION: Lily mixed a 45% copper sulfate solution and a 25% copper sulfate solution to get 100 mL of a 31% copper sulfate solution. Haw many mL of the 25% solution did she use?

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Question 386217: Lily mixed a 45% copper sulfate solution and a 25% copper sulfate solution to get 100 mL of a 31% copper sulfate solution. Haw many mL of the 25% solution did she use?
Answer by stanbon(57407) (Show Source):
You can put this solution on YOUR website!
Lily mixed a 45% copper sulfate solution and a 25% copper sulfate solution to get 100 mL of a 31% copper sulfate solution. Haw many mL of the 25% solution did she use?
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Equations:
Quantity Eq:::: x + y = 100mL
Copper Eq::::: 0.25x+0.55y = 0.31*100
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Multiply Quantity by 55
Multiply Copper by 100
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55x + 55y = 55*100
25x + 55y = 31*100
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30x = 24*100
x = 80mL (amt. of 25% solution needed in the mix)
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Cheers,
Stan H.