Question

A health food store mixes granola that costs them $4 per pound and raisins that cost them $2 per pound together to make 25 pounds of raisin granola. How many pounds of raisins should they include if they want the mixture to cost them a total of $80?

Answer 1

1) Gathering the data

$4 granola

$2 raisins

25 pounds of raisin granola

2) Let's write a system of equations, based on that:

4g +2r = 80 This equation relates the prices

g + r = 25 This one relates to the weight

4g +2r = 80

g +r = 25 x( -4) To eliminate g

4g +2r = 80

-4g -4r = -100

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-2r = -20 Divide both sides by -2

r= 10

3) So we must include a total of 10 pounds of raisin to make it cost a total of $80.