Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 2 — Practice Set 4 — Answers
Answer sheet with worked solutions for the Year 7 factors, multiples & primes worksheet.
Success TutoringWorksheetsAnswer sheetYear 7 · Mathematics · Factors, Multiples & PrimesYear 7 Prime Factorisation (Factor Trees) Worksheet — Level 2 — Practice Set 4 — Answers
Keep splitting each number into two factors until every branch ends in a prime. Write the primes from smallest to largest.
1.Use a factor tree to write 40 as a product of prime factors.
Answer: 2×2×2×5
- 40 = 2 × 20
- 20 = 2 × 10
- 10 = 2 × 5
- So 40 = 2 × 2 × 2 × 5 = 23 × 5
2.Use a factor tree to write 105 as a product of prime factors.
Answer: 3×5×7
- 105 = 3 × 35
- 35 = 5 × 7
- So 105 = 3 × 5 × 7
3.Use a factor tree to write 50 as a product of prime factors.
Answer: 2×5×5
- 50 = 2 × 25
- 25 = 5 × 5
- So 50 = 2 × 5 × 5 = 2 × 52
4.Which number has the prime factorisation 2 × 5 × 7?
Answer: 70
- 2 × 5 × 7 = 70
5.Use a factor tree to write 135 as a product of prime factors.
Answer: 3×3×3×5
- 135 = 3 × 45
- 45 = 3 × 15
- 15 = 3 × 5
- So 135 = 3 × 3 × 3 × 5 = 33 × 5
6.Use a factor tree to write 252 as a product of prime factors.
Answer: 2×2×3×3×7
- 252 = 2 × 126
- 126 = 2 × 63
- 63 = 3 × 21
- 21 = 3 × 7
- So 252 = 2 × 2 × 3 × 3 × 7 = 22 × 32 × 7
7.Use a factor tree to write 70 as a product of prime factors.
Answer: 2×5×7
- 70 = 2 × 35
- 35 = 5 × 7
- So 70 = 2 × 5 × 7
8.Which number has the prime factorisation 22 × 33?
Answer: 108
- 2 × 2 × 3 × 3 × 3 = 108
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
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