Problema Solution

The bank teller gives Mary $4.00 in dimes and nickels only. She gives Mary seven more dimes than nickels. How many dimes does she give Mary?

Answer provided by our tutors

1 nickle = 5 cents

1 dime = 10 cents

Let

n = the number of nickles, n>=0

d = the number of dimes, d>=0

She gives Mary seven more dimes than nickels:

d = 7 + n

The total value of the coins is $4.00 = 400 cents:

5n + 10d = 400

We have the following system of equations:

d = 7 + n

5n + 10d = 400

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n = 22 nickles

d = 29 dimes

The bank gave 29 dimes to Mary.