When some things go away, the group gets smaller. That is taking away, or subtracting. It undoes putting together.
Key idea
To take away, start with the whole group, remove some, and count what is left. We write $6 - 2 = 4$ and say “6 minus 2 equals 4.”
Why it works
The ones taken away are gone. Only the ones that stay are left to count.
Worked example: Birds fly away
There are 7 birds. 3 fly away. How many are left?
- Start with 7.
- Cross out 3.
- Count the rest: 1, 2, 3, 4.
- $7 - 3 = 4$
Answer: 4 birds
Common mistake
Counting the ones taken away instead of the ones left. The question asks what is left. Check: the ones left and the ones taken away together make the whole group, 4 and 3 make 7.
For grown-ups: Act it out: 5 grapes, eat 2, how many left? Ask your child to tell the story with the words “take away” and “left.”