Subtracting numbers up to 20
Subtracting is taking away. Just like with adding, there are a few different paths to the right answer. Pick the one your brain likes best.
Way 1 — counting back
Start at the bigger number, count back the smaller one.
13 − 4 → start at 13, count back: "12, 11, 10, 9"
The last number you said is your answer: 9.
Way 2 — going down to ten
If the answer would slip below ten, stop at ten on the way down.
For 14 − 6:
Go from 14 down to 10 — that is 4 steps.
You still need to take away 2 more (since 6 − 4 = 2).
10 − 2 = 8. So 14 − 6 = 8.
This trick is the mirror image of "make ten" for adding.
Way 3 — the missing piece
Sometimes it is easier to ask "how many more do I need to get to the bigger number?"
For 12 − 8:
Start at 8. How many more do I need to reach 12? Count: "9, 10, 11, 12" — that is 4.
So 12 − 8 = 4.
This trick is amazing when the two numbers are close to each other.
Things that help
- Read the problem out loud as a story. "I have 12 candies, I eat 5. How many are left?"
- Use blocks, fingers or drawn dots — anything you can really see.
- Check by adding: 12 − 5 = 7? Yes, because 7 + 5 = 12.