Subtraction
Subtract within 20 fluently — count back, think addition, and compare.
1 Subtraction means take away
When some things leave a group, we subtract. The starting amount minus what leaves equals the difference — what is left.
Example: 14 cookies − 6 cookies = 8 cookies left. Order matters: 14 − 6 is not 6 − 14.
14 − 6 = 8. Fourteen things lose six; eight remain.
2 Strategy 1: count back
Start at the bigger number and step backward. For 14 − 6: 14 … 13, 12, 11, 10, 9, 8.
12 − 4: hop back 4 from 12 → 11, 10, 9, 8.
3 Strategy 2: think addition
Every subtraction hides an addition: 12 − 5 = ? is the same as 5 + ? = 12. Count up from 5 to 12.
15 − 7: ask 7 + ? = 15. Count up 7 → 15: 8 steps, so 8.
4 “How many more” problems
“How many more” is a comparison, not a take-away — but it still subtracts: bigger − smaller.
Ann has 11 stickers, Ben has 4. How many more does Ann have? 11 − 4 = 7.
5 Common mistakes
Two traps that catch almost everyone once.
Wrong: 5 − 8 = 3 (flipping the digits). Right: subtraction is not commutative — order matters. Model 5 − 8 with objects: you cannot take 8 from 5.
Wrong: “How many more does Ann have?” → adding. Right: draw the situation: are parts joining (add) or is one group bigger than another (subtract to compare)?
6 Quick checks
Try these yourself, then reveal the answer.
7 Key points and vocabulary
| Word | What it means |
|---|---|
| Difference | The result of a subtraction; what is left. |
| Take away | Removing some from a group. |
| Count back | Stepping backward from the start number. |
| Think addition | Solving a − b by asking b + ? = a. |
| Compare | Finding how much bigger one group is: bigger − smaller. |
Remember
- Order matters: 14 − 6 is not 6 − 14.
- Count back for small take-aways; think addition for the rest.
- “How many more” means subtract: bigger − smaller.
- Check with addition: if 14 − 6 = 8, then 6 + 8 must equal 14.