Task
Show what you know about adding and subtracting fractions. You may use your fraction wall. For Questions 5–8 you must show the renaming step — the renaming is the mathematics we are checking.
Part A — Same denominators
Q1. 2/7 + 3/7 =
Q2. 7/8 - 3/8 = (simplest form: )
Part B — Spot the related denominators
Q3. Tick the pairs of denominators that are related:
- (2, 6)
- (4, 6)
- (5, 10)
- (6, 8)
Q4. Rename 3/4 as twelfths: 3/4 =
Part C — Rename, then count (show the renaming step)
Q5. 1/2 + 3/8
Renaming step: Answer:
Q6. 5/6 - 1/2
Renaming step: Answer:
Q7. 2/3 + 5/12 (your answer will pass one whole — write it as a mixed number)
Renaming step: Answer:
Q8. A jug is 9/10 full of juice. Sam pours out 3/5 of the jug. What fraction of the jug still has juice in it? Show your working and answer in a sentence.
Part D — Explain the mathematics
Q9. Zoe worked out 1/3 + 1/6 = 2/9. Explain the mistake Zoe made and show the correct answer with a diagram or fraction wall.
Q10. Why must fractions have the same denominator before you can add or subtract them? Explain in one or two sentences using the words parts and same size.
Rubric criteria (weights as a percentage of this assessment)
| Criterion | Weight | Descriptor |
|---|---|---|
| Calculating with related denominators | 30% | Adds and subtracts fractions with related denominators accurately, including answers past one whole expressed as mixed numbers, and applies the skill in a worded context with a sentence answer (Q5–Q8). |
| Equivalence and renaming | 30% | Identifies related denominators using knowledge of multiples and renames a fraction as an equivalent fraction by multiplying numerator and denominator by the same number (Q3–Q4 and the renaming step in Q5–Q8). |
| Reasoning and error analysis | 20% | Explains why fractions require same-sized parts before adding or subtracting, and diagnoses the add-the-denominators error using size reasoning or a fraction-wall diagram (Q9–Q10). |
| Same-denominator fluency | 20% | Adds and subtracts fractions with the same denominator accurately, keeping the denominator unchanged and expressing answers in simplest form where asked (Q1–Q2). |