SOLUTION: Mr. Jackson is filling planter boxes with soil. He has soil that is 19% sand, and he buys 8 pounds of a commercial potting soil that is 22% sand. He mixes some of his soil with the

Question 1101674: Mr. Jackson is filling planter boxes with soil. He has soil that is 19% sand, and he buys 8 pounds of a commercial potting soil that is 22% sand. He mixes some of his soil with the 8 pounds of commercial potting soil. The resulting soil mixture is 21% sand. How many pounds of his soil did Mr. Jackson use?
A. 12 lb
B. 4 lb
C. 2 lb
D. 8 lb
Found 2 solutions by richwmiller, josgarithmetic:
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
Let C denote the 19% solution and D denote the final 21% solution.
We have 8 lbs of 22% solution.
Using the method of alligation.
1= 21 - 22
2= 19 - 21
E.g. There are 2 parts of C for every 1 parts of D
then there are 8 parts of z, since (2/1)=8/z
x= 4= 8/(2/1) lbs of 19% solution to add to your 8 lbs of 22% solution.
y= 12= (8+4) lbs of the final 21% solution.
check
0.19 * 4 + 0.22 * 8 = 0.21*(8+4)
0.76 + 1.76 = 0.21*(12)
2.52 = 2.52
ok

22 2 8 lbs of 22% solution 21 12 lbs of 21% solution 19 1 1/2*8=4 lbs of 19% solution 3

Answer by josgarithmetic(39625) (Show Source): You can put this solution on YOUR website!
x, how much of his 19% sand soil added to mix

.
.
This can also be solved more easily because the given values allow for simple whole numbers, not far apart.
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