Question

Timmy has almost $2.00 in allowance money that he wants to spend on candy. he has two favorite candies, one selling at $0.15 a piece and one at $0.08 a piece. if he ends up spending $1.92 on 17 pieces of candy, how many $0.15 pieces of candy did timmy decide to buy?

Answer 1

Let's call
x = Amount of candy sold at $ 0.15.
y = Amount of candy sold at $ 0.08.
We must make the following system of equations:
x + y = 17
0.15x + 0.08y = 1.92
Solving the system of equations:
0.15x + 0.08 (17-x) = 1.92
0.15x-0.08x + 1.36 = 1.92
0.15x-0.08x = 1.92-1.36
0.07x = 0.56
x = 0.56 / 0.07 = 8
On the other hand,
x + y = 17
8 + y = 17
y = 17-8 = 9
Finally, Timmy bought 8 pieces of candy for $ 0.15.