Addition and Subtraction: Class 1 Study Guide
Addition joins groups to make a bigger group. Subtraction takes some away.
Suppose you have 3 mangoes and your friend gives you 2 more. You now have 5 mangoes. We write this as 3 + 2 = 5. The plus sign (+) means add and the equals sign (=) means 'is the same as'. If you eat 2 of your 5 mangoes, you have 3 left: 5 − 2 = 3. The minus sign (−) means take away.
Children first do sums with real things such as beads and counters, then with pictures, and finally with numbers only. This slow move from concrete to abstract helps understanding.
Counting on and counting back
To add, start at the bigger number and count on. For 6 + 3, say 'six… seven, eight, nine'. To subtract, count back. For 8 − 3, say 'eight… seven, six, five'. A number line is a good helper.
Number bonds
Pairs that make a number are called number bonds. The bonds of 10: 1+9, 2+8, 3+7, 4+6 and 5+5. If you know that 7 + 3 = 10, you also know that 10 − 3 = 7 and 10 − 7 = 3.
| Add | Subtract |
|---|---|
| 7 + 3 = 10 | 10 − 3 = 7 |
| 4 + 5 = 9 | 9 − 5 = 4 |
| 8 + 2 = 10 | 10 − 2 = 8 |
Story problems
Read the story, decide whether things are joining or being taken away, and write a number sentence.
Ravi has 8 marbles. He loses 3.
Losing means taking away.
8 − 3 = 5.
Ravi has 5 marbles left.
Worked examples and common mistakes
Example: 9 + 6. Make 10 first: 9 + 1 = 10, then add the remaining 5, so 15. Example: 14 − 5. Take 4 to reach 10, then take 1 more: 9. Common mistakes: counting the number you start on as 1, and adding when the story says take away. Use the same word in your answer as in the question, like 'left' for take away.
Check your understanding: model answers
1. 5 + 7 = 12. 2. 12 − 4 = 8. 3. 9 − 4 = 5 birds are left.
✨ Key Takeaways
- Add means join; subtract means take away.
- Count on from the bigger number.
- Number bonds of 10 help with many facts.
- Write answers in a sentence.
💬 Questions for Discussion & Reflection
- Find 5 + 7.
- Find 12 − 4.
- There are 9 birds on a tree and 4 fly away. How many are left?