SOLUTION: how many quarters and dimes of 40 coins does it take to make 7.75

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Question 950750: how many quarters and dimes of 40 coins does it take to make 7.75
Answer by erica65404(394) About Me  (Show Source):
You can put this solution on YOUR website!
x=quarters y=dimes

Start out by making 2 equations.

You want to first find the equation for how many dimes and quarters there are.
x%2By=40

Then you make an equation for the amount of money involved.
quarters are $.25 and dimes are $.10. in order to find the total amount of money you would take the # of dimes you have and multiply that by .10. then you would take the # of quarters you have and multiply them by .25. then you would add it up to find the total amount of change. Since we are given the amount of money they have, you can use the below equation to find the dimes and quarters.
.25x%2B.10y=7.75

Then use the substitution method to find x or y. I will solve for y first.

x%2By=40
x=40-y

then plug this into the other equation.

.25x%2B.10y=7.75
.25%2840-y%29%2B.10y=7.75
10-.25y%2B.10y=7.75
-.15y=-2.25
y=15

There are 15 dimes and 25 quarters.