Word problems are little stories. Before you add or subtract, picture what happens. This builds on How Many More? How Many Fewer? and the stories you solved in Grade 1.
- Add to: some more come.
- Take from: some go away.
- Put together: two parts make a whole.
- Compare: how many more, or how many fewer?
Por qué funciona
A tape diagram shows the parts and the whole. If you know both parts, add to find the whole. If you know the whole and one part, subtract to find the other part. The picture decides what to do, not a single word in the story.
Ejemplo resuelto: The start is missing
Some birds sat on a fence. Then 18 more birds landed. Now there are 45 birds. How many were on the fence at first?
- The story says “more,” but the start is the missing part.
- Parts: ? and 18. Whole: 45. So $? + 18 = 45$.
- Find the missing part: $45 - 18 = 27$.
- Check: $27 + 18 = 45$.
Respuesta: 27 birds
Ejemplo resuelto: “Fewer,” but you add
Ana has 34 stickers. She has 12 fewer stickers than Ben. How many stickers does Ben have?
- “Ana has 12 fewer than Ben” means Ben has 12 more than Ana.
- Ben’s amount is the bigger one: $34 + 12 = 46$.
Respuesta: 46 stickers
Idea clave
Picture the story and find the whole and the parts. Whole missing: add. Part missing: subtract. Put your answer back into the story to check it.
Error común
Choosing the operation from a key word, like adding whenever you see “more.” In the bird story, “more” is there but you subtract. Check: put your answer into the story and read it again. Does it make sense?
Grown-up tip: Act the story out with toys, and ask your child to draw the tape before doing any math.