SOLUTION: Ms. Butler is filling planter boxes with soil. She has soil that is 28% sand, and she buys 6 pounds of a commercial potting soil that is 33% sand. She mixes some of her soil with

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Question 400613: Ms. Butler is filling planter boxes with soil. She has soil that is 28% sand, and she buys 6 pounds of a commercial potting soil that is 33% sand. She mixes some of her soil with the 6 pounds of commercial potting soil. The resulting soil mixture is 31% sand. How many pounds of her soil did Ms. Butler use?
Answer by josmiceli(9664) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
(sand in final mixture)/(sand + soil in final mixture) = 31%
Let x = pounds of her soil she used
given:
.28x = pounds of sand in her soil
.33%2A6+=+1.98 pounds of sand in commercial potting soil
--------------------------
%28.28x+%2B+1.98%29%2F%286+%2B+x%29+=+.31
.28x+%2B+1.98+=+.31%2A%286+%2B+x%29
.28x+%2B+1.98+=+1.86+%2B+.31x
.03x+=+.12
x+=+4
She needs 4 pounds of her soil
check:
%28.28%2A4+%2B+1.98%29%2F%286+%2B+4%29+=+.31
%281.12+%2B+1.98%29%2F10+=+.31
3.1%2F10+=+.31
3.1+=+3.1
OK