SOLUTION: a contractor mixes concrete from bags of pre-mix for small jobs. how many bags with 6% cement should he mix with 10 bags of 16.2 cement to produce a mix containing 12% cement?

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Question 247845: a contractor mixes concrete from bags of pre-mix for small jobs. how many bags with 6% cement should he mix with 10 bags of 16.2 cement to produce a mix containing 12% cement?
Found 2 solutions by stanbon, richwmiller:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
a contractor mixes concrete from bags of pre-mix for small jobs. how many bags with 6% cement should he mix with 10 bags of 16% cement to produce a mix containing 12% cement?
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Equation:
cement + cement = cement
0.06x + 0.16*10 = 0.12(x+10)
Multiply thru by 100 to get:
6x + 16*10 = 12x+12*10
6x = 4*10
x = 6.67 or 6 2/3 bags (# of bags of 6% cement needed for the mixture)
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Cheers,
Stan H.

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
let x equal number of bags of 6 percent cement
.06x+10(.162)=(10+x)(.12)
solve for x