Missing-number problems to 100 – Grade 2
Missing-number problems to 100 for Grade 2: use inverse operations to find the unknown and substitute to check. Examples and practice.
🎯 What you will learn
- ✓Recognise the operation
- ✓Use the inverse
- ✓Substitute to check
💡 How it works
Learn “Missing-number problems to 100 – Grade 2” in small steps: understand the method first, then practise with a worksheet or online test.
How it works
💡 Rule: the box is the unknown number. Use the inverse operation and substitute to check.
A missing-number problem is an inverse operation. In □ + 36 = 70 ask: what must be added to 36 to make 70?
Work from the known part to the total: 36 + 4 = 40, then + 30 = 70. The missing number is 34.
For □ − 18 = 25, use addition: 25 + 18 = 43.
🧩 See the method
✍️ Worked examples
Worked examples 1
□ + 36 = 70
- 1.From 36 to 40 is 4.
- 2.From 40 to 70 is 30.
- 3.4 + 30 = 34
✓ 34
Worked examples 2
□ − 18 = 25
- 1.Find the start number.
- 2.25 + 18 = 43
- 3.Check: 43 − 18 = 25
✓ 43
⚠️ Common mistakes
- • Calculating the known number instead of the gap.
- • Forgetting the check.
📝 Try it yourself
1.
□ + 27 = 50
Show answer
23
2.
□ + 48 = 80
Show answer
32
3.
□ − 15 = 31
Show answer
46
4.
□ − 24 = 40
Show answer
64
5.
19 + □ = 60
Show answer
41
6.
75 − □ = 30
Show answer
45
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FAQ
How do I check □ + 36 = 70?
Insert 34: 34 + 36 = 70.
What does □ − 18 = 25 mean?
Find the start number: 25 + 18 = 43.