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P1 Subtraction within 20: Paper 4 Error Clinic
P1 Subtraction within 20: Paper 4 Error Clinic
This paper targets common slips: break-ten and taking from 20, then column form, change and finding a missing number, before two-step work and comparison, and finally a correction where 12 minus 7 was given as 6. Every item has an answer and a one-line note.
Direct answers Items 01 to 03 rebuild break-ten and taking from 20, 04 to 06 cover column form, change and a missing number, 07 to 09 are two-step and comparison items, and 10 corrects a wrong answer.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: P1 Subtraction within 20 |
| Level | P1 |
02 Questions (10 items)
- FoundationWork out 18 – 9.
- FoundationWork out 16 – 7.
- FoundationWork out 20 – 6.
- IntermediateUse column form to work out 17 – 8.
- IntermediateA pencil costs $7. You pay with $20. How much change do you get?
- IntermediateA number minus 6 gives 8. What is the number?
- ChallengeWork out 20 – 8 – 7.
- ChallengeAre 15 – 6 and 14 – 5 the same?
- ChallengeWhat is 19 – 4? Then add 3 to the result.
- Error redoCorrect this answer: 12 – 7 = 6.
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 9. | Break ten: 18 minus 8 is 10, then minus 1 leaves 9. |
| 2 | 9. | 16 minus 6 is 10, then minus 1 leaves 9. |
| 3 | 14. | The ones digit of 20 is 0, so borrow ten: 10 minus 6 is 4, then add the other 10 to get 14. |
| 4 | 9. | The ones digit 7 is smaller than 8, so borrow ten: 10 minus 8 is 2, then 2 plus 7 gives 9. |
| 5 | $13. | 20 minus 7 is 13, and 13 plus 7 gives 20 again, so the change is correct. |
| 6 | 14. | Work backwards with addition: 8 plus 6 is 14, and 14 minus 6 is 8 again. |
| 7 | 5. | 20 minus 8 is 12, then minus 7 leaves 5; 8 plus 7 is 15 and 20 minus 15 is also 5. |
| 8 | Yes, both are 9. | Taking 1 away from both numbers keeps the difference the same, so both answers are 9. |
| 9 | 15 and 18. | Work in order: 19 minus 4 is 15, then plus 3 gives 18. |
| 10 | 5. | Break ten: 12 minus 2 is 10, then minus 5 leaves 5; 6 comes from taking away 6 instead of 7. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
P1 subtraction within 20 paper 4: ten answered items that drill out common mistakes.Tutor Registration →
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