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P4 HCF and LCM: Paper 4 Error Clinic
P4 HCF and LCM: Paper 4 Error Clinic
This is the error clinic: the common slips are gathered for one more round, including mixing up the H.C.F. and the L.C.M., sharing against meeting again, finding the missing number and the largest square.
Direct answers Answers: 1 8; 2 18; 3 15; 4 60; 5 H.C.F. 14, L.C.M. 84; 6 24; 7 12 packs of 4 and 3; 8 12 days; 9 side 24 cm, 12 squares; 10 4 is the H.C.F. and the L.C.M. is 24.
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: P4 HCF and LCM |
| Level | P4 |
02 Questions (10 items)
- FoundationFind H.C.F.(16, 24).
- FoundationFind L.C.M.(6, 9).
- FoundationFind H.C.F.(30, 45).
- IntermediateFind L.C.M.(12, 15).
- IntermediateFind H.C.F.(28, 42) and L.C.M.(28, 42).
- IntermediateTwo numbers have H.C.F. 6 and L.C.M. 72. One is 18; what is the other?
- ChallengeHow many identical packs can be made from 48 sweets and 36 biscuits?
- ChallengeA works every 4 days and B every 6 days. Both work today; when do they next work together?
- ChallengeA 96 cm by 72 cm card is cut into the largest equal squares. What is the side and how many squares?
- Error redoA pupil writes “L.C.M.(8, 12) = 4”. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 8. | The largest number dividing both 16 and 24 is 8. |
| 2 | 18. | The multiples of 6 and 9 first meet at 18. |
| 3 | 15. | Both divide by 15, and no larger common factor exists. |
| 4 | 60. | 12 times 15 divided by the H.C.F. 3 gives 60. |
| 5 | The H.C.F. is 14 and the L.C.M. is 84. | The greatest common factor is 14, and 28 times 42 divided by it gives 84. |
| 6 | 24. | The product of the numbers is H.C.F. times L.C.M., so 6 times 72 divided by 18 is 24. |
| 7 | 12 packs, each with 4 sweets and 3 biscuits. | Sharing fully needs the H.C.F., which is 12. |
| 8 | 12 days later. | Meeting again needs the L.C.M., which is 12. |
| 9 | Side 24 cm, 12 squares. | The side is the H.C.F. 24, then 4 times 3 gives 12 squares. |
| 10 | The H.C.F. was written instead: 4 is the H.C.F. and the L.C.M. is 24. | A common multiple is never smaller than either number, so 4 cannot be the L.C.M. |
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.
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