Systems of equations

Question

Jace has $2.15 in nickels and dimes. If he has 7 more nickels than dimes, how many of each coin does he have?

Answer 1

Let's do this using cents (pennies).

Let D = # of times

N = # of nickels

N = D + 7 (number of nickels is 7 more then number of dimes).

Now use the fact that there are 215 pennies in total. Each time is 10 pennies and each nickel is 5 pennies.

10D + 5N = 215

Using the first equation substitute D + 7 for N into the second equation (substitution method).

10D +5(D + 7) = 215

10D + 5D + 35 = 215

15D = 180

D = 12

N = 12 + 7 = 19

12 dimes = $1,20

19 nickels = $0.95

Total $2.15 (check)