Adding to 100
We can add small numbers and tens to make numbers up to 100. The trick is to keep the tens and the ones apart. First add the tens together, then add the ones together, and put them back as one number. Adding whole tens is easy, like 20 + 30 = 50.
Key idea
Add tens with tens, add ones with ones. 25 + 4: keep 20, then 5 + 4 = 9, so the answer is 29.
Add step by step
Worked example
Add 12 + 3. Keep the ten (10). Now add the ones: 2 + 3 = 5. Put them back: 10 and 5 make 15. So 12 + 3 = 15.
Remember
- Keep tens and ones apart.
- Add ones first, then tens.
- Whole tens are quick.
- Check by counting on.