Ordering Numbers 51-100 Answer Key

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📚 Lower Ability Answers (Numbers 51-70)

1. Order these 5 numbers from smallest to largest: 67, 52, 61, 58, 65

Answer: 52, 58, 61, 65, 67

Explanation: Look at the tens digit first. All numbers start with 5 or 6. Numbers starting with 5 come before numbers starting with 6. For numbers with the same tens digit, look at the units digit: 52 (2 units), 58 (8 units), then 61 (1 unit), 65 (5 units), 67 (7 units).

2. Order these 5 numbers: 69, 54, 63, 56, 70

Answer: 54, 56, 63, 69, 70

Teaching tip: Use a number line to help pupils visualise the order. Point out that 70 is the largest because it has 7 tens and 0 units.

✏️ Middle Ability Answers (Error Correction)

3. Find and correct the errors in this sequence: 54, 57, 56, 59, 62, 61, 65, 67

Incorrect sequence: 54, 57, 56, 59, 62, 61, 65, 67

Correct sequence: 54, 56, 57, 59, 61, 62, 65, 67

Errors found: 56 and 57 were swapped (56 comes before 57), and 61 and 62 were swapped (61 comes before 62). When the tens digits are the same, always check the units digit to put them in order.

4. Correct this sequence: 73, 71, 75, 74, 78, 76, 80, 79

Correct sequence: 71, 73, 74, 75, 76, 78, 79, 80

Strategy: All numbers have 7 or 8 tens. Group the 70s together first (71, 73, 74, 75, 76, 78, 79), then add 80 at the end.

🌟 Higher Ability Answers (Create and Justify)

5. Example 10-number ascending sequence with justification:

Sample sequence: 53, 58, 64, 67, 72, 75, 81, 86, 93, 98

Justification: This sequence is correct because each number is larger than the one before it. I checked by comparing tens digits first (5, 5, 6, 6, 7, 7, 8, 8, 9, 9), then units digits when tens are the same. The sequence increases steadily from 53 to 98.

6. Peer-check instructions for pupils:

How to check your partner's work:

1. Read each number from left to right

2. Check: Is each number bigger than the one before?

3. If tens digits are the same, is the units digit getting bigger?

4. Circle any mistakes and explain to your partner

5. Help them fix any errors together

7. Challenge extension: Numbers with gaps

Example sequence: 55, 61, 67, 73, 79, 85, 91, 97

Pattern: Each number increases by 6 (adding 6 each time)