SOLUTION: A bag containing 5 pounds of mixed nuts is 15% peanuts. How many pounds of peanuts must be added to the bag to produce a mixture that is 25% peanuts?

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Question 716020: A bag containing 5 pounds of mixed nuts is 15% peanuts. How many pounds of peanuts must be added to the bag to produce a mixture that is 25% peanuts?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Assign Variables:
M=amount of mixture before addition, 5 pounds
c=percent of mixture as peanuts before addition, 15%
p=how many pounds of peanuts to add, unknown
r=resulting percent peanuts after adding p pounds, 25%

Create Equation:
highlight%28%28M%2Ac%2Bp%2A100%29%2F%28p%2BM%29=r%29, the factor of 100 with p is because p is at 100%.
Solve for p.
.
skipping the steps here
.
highlight%28p=M%28r-c%29%2F%28100-r%29%29

Now you simply substitute the given values to calculate p.