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Calvin has 13 coins , all of which are quarters and nickels. The coins are worth $2.45. How many of each coin does Calvin have ?

 Apr 13, 2020
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q=quarters

n=nickles

 

q+n=13

.25q+.05n=2.45 (multiply by 100)

25q+5n=245

n=-q+13

 

25q+5(-q+13)=245 (Substition)

25q-5q+65=245

20q+65=245 (Substract 65 from both sides)

20q=180

q=9 

9+n=13

n=4

 

To check

.25(9)+.05(4)=2.45

 Apr 13, 2020

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