Mental Subtraction Strategies

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Date:

📚 Part 1: Multiple Choice — Use mental strategies

1. What is 86 − 7? Think: count back on your number line.

2. What is 100 − 47? Which mental strategy is quickest?

3. What is 605 − 8? Use counting back or make small jumps.

597

598

607

4. Check all problems that are best solved using complements to 10 or 100:

100 − 47

86 − 7

500 − 279

73 − 8

5. Use counting back mentally: 54 − 9 = _______

Briefly write the steps you used (one or two lines):

6. Use complements: Write the number sentence showing the complement for 100 − 68 (example format: 68 + ____ = 100)

Then give the answer: 100 − 68 = _______

7. Real life: You buy something for $38 and pay with $50. Mentally work out the change: $_______

8. Temperature: If the high was 24°C and it drops by 7°C, what is the new temperature? _______°C

Which strategy did you use? (brief)

9. Challenge for a partner: Create a two-step subtraction under 1000 (write the number sentence) and find the answer.