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soil (i just asked this but forgot to include my email on the last one)

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Mr. Butler is filing planter boxes with soil.  He has soil that is 30% sand, and he buys 9 pounds of a commercial potting soil that is 18% sand.  He mixes some of his soil with the 9 pounds of commercial potting soil.  The resulting soil mixture is 21% sand.  How many pounds of his soil did Mr. Butler use?

ForensicGirl  Feb 23, 2017
edited by Guest  Feb 23, 2017
edited by Guest  Feb 23, 2017
edited by Guest  Feb 23, 2017
edited by Guest  Feb 23, 2017
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Amt  of 18% soil + unknown amt of 30% soil = total soil at 21%

9 (.18) + x (.30) =  ( 9 + x).21   simplify

1.62 + .30x = 1.89 + .21x    subtract 1.62, .21x  from both sides

.09x  = .27    divide both sides by   .09

x  = 3 lbs.  of 30% soil

CPhill  Feb 23, 2017

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