Question

Tim’s piggy bank contains dimes and nickels worth $5.50. He has 70 coins in all. Use substitution to find out the numbers of each coin Tim has.

Answer 1

Let x = number of dimes
Let y = number of nickels

x + y = 70

0.10x + 0.05y = 5.50

Substituting y = 70 - x into the second equation:

0.10x + 0.05(70 - x) = 5.50

Solving for x:

0.10x + 3.50 - 0.05x = 5.50

0.05x = 2

x = 40

y = 70 - 40 = 30

Tim has 40 dimes and 30 nickels.