Stage 10 of 20
Two-Digit Mental Subtraction
Subtract two-digit numbers by counting up, decomposing, or compensating — pick the strategy that keeps numbers friendly.
Prefer counting up when numbers are close
For 81 − 67, count from 67 to 81: +3 to 70, +11 to 81 → 14. When numbers are far apart, subtract tens then ones, or round and adjust.
Why this mental math skill matters
Mental subtraction supports change-making, time calculations, and error checking. Counting up is especially powerful when numbers are close.
Worked examples
Study each example slowly. Say the steps aloud — verbal rehearsal strengthens mental arithmetic memory.
81 − 67
- 67 + 3 = 70.
- 70 + 11 = 81.
- 3 + 11 = 14.
Answer: 14
74 − 39
- 74 − 40 = 34.
- You subtracted 1 too many, so add 1 back.
- 35.
Answer: 35
92 − 45
- 92 − 40 = 52.
- 52 − 5 = 47.
Answer: 47
Tips for success
- If numbers are close, count up.
- If subtracting a near ten, round and adjust.
- Check by adding the difference back.
Common mistakes to avoid
- Counting back across many tens without landmarks.
- Subtracting digits out of place value order.
How to practice this stage
Sort problems into “close numbers” (count up) vs “far apart” (decompose or compensate). Practice both families.
Interactive practice
Stage 10 Drill
Find the difference between two two-digit numbers.
Solve
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FAQ: Two-Digit Mental Subtraction
What is the easiest way to subtract two-digit numbers mentally?
Often counting up from the smaller number, or subtracting tens then ones with clear checkpoints.
How do I check a mental subtraction?
Add your answer to the number you subtracted; you should return to the starting number.