Adding and Subtracting Within 20: Grade 1 Study Guide
In Grade 1, children move from counting every object to using smart strategies that make facts fast and easy.
Grade 1 children learn to add and subtract within 20 and to solve story problems about adding to, taking from, putting together and comparing. The aim is fluency within 10 by the end of the year, which means knowing facts like 6 + 3 and 9 − 4 quickly and accurately.
The way to fluency is through strategies, not memorizing alone. A child who understands why 8 + 5 = 13 can rebuild the fact if they forget it. The strategies below also lay the groundwork for mental maths in later grades.
Strategy 1: counting on
Start at the larger number and count up. For 4 + 3, say 'four… five, six, seven'. Hold the smaller number on your fingers so you know when to stop. For subtraction, count back or count up to the bigger number. For 9 − 6, think 'how many do I add to 6 to reach 9?' (3).
Strategy 2: make a ten
To add 8 + 5, take 2 from the 5 to make 8 into 10. Now 10 + 3 = 13. This 'make ten' strategy works for all facts with a 9 or 8 and is very powerful because our number system is built on tens.
8 needs 2 more to make 10.
5 = 2 + 3.
8 + 2 = 10.
10 + 3 = 13.
Strategy 3: doubles and fact families
Doubles (3 + 3, 4 + 4, 5 + 5) are easy to remember and help with near doubles: 6 + 7 is double 6 plus 1, which is 13. A fact family uses the same three numbers: 7, 5 and 12 give 7 + 5 = 12, 5 + 7 = 12, 12 − 5 = 7 and 12 − 7 = 5. Knowing one fact gives you the others.
| Strategy | Good for | Example |
|---|---|---|
| Count on | Adding 1, 2 or 3 | 9 + 2 → 10, 11 |
| Make ten | Facts with 8 or 9 | 9 + 6 → 10 + 5 = 15 |
| Doubles | Matching numbers | 7 + 7 = 14 |
| Near doubles | Numbers one apart | 6 + 7 = 12 + 1 = 13 |
| Think addition | Subtraction | 13 − 8 → 8 + ? = 13 |
Story problems and the equals sign
Read the story, draw it, then write an equation. 'Maya had 9 stickers and got 4 more' is 9 + 4 = 13. 'There were 14 apples and 6 were eaten' is 14 − 6 = 8. In Grade 1, children also learn that the equals sign means 'is the same amount as'. So 7 = 4 + 3 and 5 + 2 = 3 + 4 are both true. A common mistake is to read the = sign as 'the answer comes next'.
Check your understanding: model answers
1. Take 1 from the 7 to make 9 into 10: 10 + 6 = 16. 2. 6 + 8 = 14, 8 + 6 = 14, 14 − 6 = 8, 14 − 8 = 6. 3. Yes. Both sides equal 8, so the = sign shows the same amount on each side.
✨ Key Takeaways
- Counting on, making ten and doubles make facts quick.
- A fact family uses the same three numbers.
- The equals sign means 'the same amount as'.
- Draw story problems before writing the equation.
💬 Questions for Discussion & Reflection
- Use make a ten to find 9 + 7.
- Write the four facts in the family for 6, 8 and 14.
- Is 5 + 3 = 4 + 4 true? Explain.