Math

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Lee has 35 dimes and quarters that total \$5.00. Solve the system of equations to find how many dimes and how many quarters he has.
d+q=35
0.1d+0.25q=5

• Math -

d+q=35 ....(1)
0.1d+0.25q=5
multiply the second by 20 to get
2d+5q=100 ....(2)
Substitute d=35-q from (1)
70-2q+5q=100
3q=30
q=10
d=25

Another way to calculate (mentally) is as follows:
Assume all dimes: 35*0.1=3.5
There is \$1.50 available to change quarters for dimes at 15 cents a piece. So we change 10 of them to get 10 quarters and (35-10)=25 dimes.

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