Here are five small puzzles, solved step by step. Read slowly and try each one before you peek.
Example 1 — adding without crossing the ten
Find 6 + 3.
6 + 3 = 9.
Both numbers are small, the answer stays under ten. Easy as pie.
Worked examples — addition and subtraction within 20
Example 2 — adding with the make-ten trick
Find 7 + 6.
Take 3 from the 6 to make the 7 into 10.
7 + 3 = 10. Then 10 + 3 = 13.
So 7 + 6 = 13.
Example 3 — subtracting without crossing the ten
Find 18 − 5.
18 − 5 = 13.
The ones digit drops from 8 to 3. The tens digit stays at 1.
Example 4 — subtracting with the down-to-ten trick
Find 15 − 8.
Go from 15 down to 10 — that is 5 steps.
You still need to take 3 more (because 8 − 5 = 3).
10 − 3 = 7. So 15 − 8 = 7.
Example 5 — find the missing number
What goes in the box? 9 + ☐ = 14.
Start at 9. Count up to 14: "10, 11, 12, 13, 14" — that is 5 steps.
The box is 5.
Check: 9 + 5 = 14. Correct!
Want more practice
- Try Addition & subtraction on the level "Up to 20".
- Try Pyramid to chain several sums together.
- Try Find the right problem to spot the calculation that gives a target answer.