Money stories use adding and subtracting with ¢ and \$. You know how to count money and how to solve word problems.
Por qué funciona
Change is the money you get back. When you pay \$1 (100¢) for something that costs 63¢, the 100¢ is the whole and 63¢ is one part. The change is the other part: $100 - 63$.
Ejemplo resuelto: Cost together
A pencil costs 35¢ and an eraser costs 48¢. How much for both?
- Together means add: $35 + 48$.
- Ones: $5 + 8 = 13$, a new ten. Tens: $3 + 4 + 1 = 8$.
Respuesta: 83¢
Ejemplo resuelto: Change from a dollar
A snack costs 63¢. You pay with \$1. How much change do you get?
- \$1 is 100¢.
- Count up from 63: +7 to 70, then +30 to 100.
- $7 + 30 = 37$.
Respuesta: 37¢
Ejemplo resuelto: Dollars
Sam has \$20. He buys a book for \$13. How much money is left?
- Spending takes money away: $20 - 13 = 7$.
Respuesta: \$7
Idea clave
Use the same unit, all cents or all dollars, then add or subtract as the story says. \$1 is 100¢.
Error común
Mixing dollars and cents, like thinking \$1 and 25¢ is 26¢. A dollar is 100¢, so \$1 and 25¢ is 125¢, written \$1.25. Check: is the total more than a dollar?
Grown-up tip: At the store, ask your child to figure out the change before the cashier does.