Year 2 · Mathematics
Addition and subtraction for Year 2: strategies for two-digit numbers
In the early years, students move from counting objects to using mental strategies. Knowing a few smart strategies makes adding and subtracting two-digit numbers faster and more reliable.
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Try asking: “How do I add 46 + 37?”
Counting on from the bigger number
For 9 + 4, start at 9 and count on 4 more: 10, 11, 12, 13. Starting from the bigger number means fewer counts.
Making ten
Numbers that add to ten are called friends of ten (1 and 9, 2 and 8, 3 and 7, 4 and 6, 5 and 5). To add 8 + 5, take 2 from the 5 to make 10, then add the 3 left over: 8 + 5 = 13.
Splitting into tens and ones
To add 27 + 15, add the tens (20 + 10) and the ones (7 + 5) separately, then put them together.
Subtracting by counting up
Subtraction can mean taking away, or finding the difference between two numbers. For 53 − 18, it can be easier to count up from 18 to 53: 18 up to 20 is 2, and 20 up to 53 is 33, so the difference is 35.
Worked examples
What is 27 + 15?
- Tens: 20 + 10 = 30.
- Ones: 7 + 5 = 12.
- Combine: 30 + 12 = 42.
Answer: 42
What is 53 − 18?
- Count up from 18 to 20: that's 2.
- Count up from 20 to 53: that's 33.
- Add the jumps: 2 + 33 = 35.
Answer: 35
What is 46 + 38?
- Tens: 40 + 30 = 70.
- Ones: 6 + 8 = 14.
- Combine: 70 + 14 = 84.
Answer: 84
Common mistakes to watch for
- Forgetting to carry the extra ten when the ones add to 10 or more.
- Subtracting the smaller digit from the bigger one in each column, whichever number it belongs to.
Practice questions
Try these, then reveal the answers. For more questions with hints, use the tutor.
1. What is 34 + 25?
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59
2. What is 48 + 16?
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64
3. What is 70 − 23?
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47
4. What is 61 − 29?
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32
5. What is 9 + 7?
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16