SOLUTION: How many gallons of a plant food that is 9% nitrogen must be combined with another plant food that is 25% nitrogen to make 10 gal. of a solution that is 15% nitrogen?

Question 74733This question is from textbook Introductory Algebra
: How many gallons of a plant food that is 9% nitrogen must be combined with another plant food that is 25% nitrogen to make 10 gal. of a solution that is 15% nitrogen? This question is from textbook Introductory Algebra

Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=the number of gal of 9% plant food
Then 10-x=the number of gal of 25% plant food
Now we know the amount of pure nitrogen before the mixture takes place must equal the amount of pure nitrogen after the mixture takes place. So our equation to solve is:
0.09x+0.25(10-x)=0.15(10) get rid of parens
0.09x+2.5-0.25x=1.5 subtract 2.5 from both sides
0.09x+2.5-2.5-0.25x=1.5-2.5 collect like terms
-0.16x=-1 divide both sides by -0.16
x=6.25 gal ---------------of the 9% plant food must be combined
ck
0.09(6.25)+0.25(3.75)=0.15(10)
0.5625+0.9375=1.5
1.5=1.5

Hope this helps---ptaylor

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