Lizzy: Antonella has ten Canadian coins in her purse that are either loonies or toonies. A loonie equals $1 and a toonie equals $2. If she bought a $3 Frappuccino and still has $11, how many toonies did she initially have?.
Me: Hmmm, let me think. I think this is the detailed solution:
If Antonella spent $3 and now has $11, that means initially she had $3 + $11 = $14. Let the number of loonies Antonella had be L and the number of toonies be T. Initially she had in her purse a total of 1L + 2T = $14. We also know that she had 10 coins in total or 10 = L + T. That means initially she had T = 10 - L toonies. Combining both equations we know that 14 = 1L + 2 * (10 - L). If we multiply through the parentheses, we get 14 = 1L + 20 - 2L. If we combine the variables on one side and the constants on another, we get - 6 = - 1L or L = 6. Knowing the value of L, we can solve for T = 10 - L = 10 - 6 = 4. Final answer: 4.