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could you please show how you did it, i have a whole bunch more i have to do and i dont know how to do them.

17. A container is partially filled with 12 liters of whole milk containing 4% butterfat. How much 1% milk must be added to get a mixture that is 2% butterfat?

18. An 80-pound grass seed mixture is 30% bluegrass seed. How many pounds of seed containing no bluegrass seed (0%) should be added to the seed mixture for a resulting blend that is 20% bluegrass seed?

2007-12-12 08:20:32 · 2 answers · asked by Anonymous in Science & Mathematics Mathematics

2 answers

PROBLEM 17:

Let x be the amount of 1% milk to add.

"12 liters of 4%" + "x liters of 1%" = "(12 + x) liters of 2%"

The equation should be:
12(4%) + x(1%) = (12 + x)(2%)

But you can just multiply everything by 100 to get rid of the percent signs:
12(4) + x(1) = (12 + x)2

48 + x = (12 + x)2
48 + x = 24 + 2x
24 = x

So you need to add 24 liters of the 1% milk. (Note: the final mixture will be 36 liters of 2%).

PROBLEM 18:

Same method...
80(30%) + x(0%) = (80 + x)(20%)

80(30) + x(0) = (80 + x)20

2400 + 0 = 1600 + 20x
800 = 20x
40 = x

So you must add 40 pounds of 0% bluegrass seed.

2007-12-12 08:28:28 · answer #1 · answered by Puzzling 7 · 0 0

They all work the same way.

Let x be the amount of 1% milk then the amount of butterfat is

12 * .04 + x * .01

Now we know that the new volume ( liters) will be 12 + x so the new percent of butterfat is (12 *.04 + x * .01) / ( 12 + x) = .02

Now solve for x

For 18) do the same thing let x be the amount of 0% bluegrass

Then (80 * .30 + x * 0) / ( 80 + x) = .20 Solve for x. Notice that this one is easier because thanks to the 0% one of the terms becomes zero.

2007-12-12 16:29:00 · answer #2 · answered by rscanner 6 · 0 0

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