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P4 Maths: Adding and Subtracting Fractions, Paper 4 (Error redo)
P4 Maths: Adding and Subtracting Fractions, Paper 4 (Error redo)
Ten redo items on the classic P4 mistakes: adding numerators and denominators, forgetting to convert to a common denominator, and borrowing wrongly.
What is the most common fraction mistake? Adding the numerators and the denominators together. Convert to a common denominator first, add or subtract only the numerators, then simplify.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: P4 Maths: Adding and Subtracting Fractions |
| Level | Level: Error redo |
02 Questions (10 items)
- FoundationWork out 3/8 + 1/8.
- FoundationWork out 7/9 − 4/9.
- FoundationWork out 1 − 3/7.
- FoundationWork out 2/5 + 1/2.
- IntermediateWork out 3/4 + 5/6.
- IntermediateWork out 5/6 − 3/8.
- IntermediateWork out 2 1/3 + 1 3/4.
- ChallengeWork out 3 1/2 − 1 3/4.
- ChallengeA jug holds 2 3/4 L of juice. 5/8 L is drunk, then 1/2 L is added. How much juice is in the jug now?
- Error redoA student writes 1/2 + 1/3 = 2/5. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | = 1 (that is 1/2) | Same denominator: add the numerators and keep the denominator. |
| 2 | = 1 (that is 1/3) | Same denominator: subtract the numerators and keep the denominator. |
| 3 | = 4/7 | Write 1 as 7/7 first, then subtract. |
| 4 | = 9/10 | Use tenths: 4/10 + 5/10. |
| 5 | = 19/12 (that is 1 7/12) | Use twelfths: 9/12 + 10/12. |
| 6 | = 11/24 | Use twenty-fourths: 20/24 − 9/24. |
| 7 | = 4 1/12 | Add the whole numbers, then the fractions in twelfths (4/12 + 9/12) and carry one. |
| 8 | = 1 3/4 | Borrow one from the whole number: change 3 1/2 into 7/2 and subtract 7/4. |
| 9 | = 2 5/8 L | Subtract then add, working in eighths. |
| 10 | It adds numerators and denominators directly. Convert first: 3/6 + 2/6 = 5/6. | Fractions with different denominators must be converted to a common denominator, and a sum cannot be smaller than its parts. |
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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