Some stories need two steps. You will use what you know about writing equations and estimating to plan, solve and check.
Por qué funciona
In a two-step problem, the answer to the first step is a tool, not the answer. The question tells you what to find at the end. Working backward from the question shows what you need first: to know what is left, you first need how many there were.
Idea clave
Read the question. Find the number you need first. Use it to answer the question. Then check: is the answer about the size you expected, and does it answer the question asked?
Ejemplo resuelto: Buy, then give away
Leo buys 3 packs of 8 stickers. He gives 5 to his sister. How many does he have now?
- Step 1: stickers bought: $3 \times 8 = 24$.
- Step 2: $24 - 5 = 19$.
- Check: fewer than 24, since he gave some away.
Respuesta: $19$ stickers
Ejemplo resuelto: Change from a bill
Maya buys 4 books for \$6 each. She pays with a \$50 bill. How much change does she get?
- Step 1: cost: $4 \times 6 = 24$, so \$24.
- Step 2: change: $50 - 24 = 26$, so \$26.
- Check: $24 + 26 = 50$.
Respuesta: \$26
Ejemplo resuelto: Take away, then share
There are 30 cookies. 6 are eaten. The rest are shared equally by 4 friends. How many does each friend get?
- Step 1: cookies left: $30 - 6 = 24$.
- Step 2: share: $24 \div 4 = 6$.
- Check: $4 \times 6 + 6 = 30$.
Respuesta: $6$ cookies
Error común
Stopping after the first step. In the sticker problem, 24 is how many Leo bought, not how many he has now. Before you finish, read the question again and ask: does my number answer it?