Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 2 — 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 — 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 105 as a product of prime factors.
Answer: 3×5×7
- 105 = 3 × 35
- 35 = 5 × 7
- So 105 = 3 × 5 × 7
2.Use a factor tree to write 30 as a product of prime factors.
Answer: 2×3×5
- 30 = 2 × 15
- 15 = 3 × 5
- So 30 = 2 × 3 × 5
3.Use a factor tree to write 200 as a product of prime factors.
Answer: 2×2×2×5×5
- 200 = 2 × 100
- 100 = 2 × 50
- 50 = 2 × 25
- 25 = 5 × 5
- So 200 = 2 × 2 × 2 × 5 × 5 = 23 × 52
4.Which number has the prime factorisation 3 × 72?
Answer: 147
- 3 × 7 × 7 = 147
5.Use a factor tree to write 196 as a product of prime factors.
Answer: 2×2×7×7
- 196 = 2 × 98
- 98 = 2 × 49
- 49 = 7 × 7
- So 196 = 2 × 2 × 7 × 7 = 22 × 72
6.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
7.Use a factor tree to write 42 as a product of prime factors.
Answer: 2×3×7
- 42 = 2 × 21
- 21 = 3 × 7
- So 42 = 2 × 3 × 7
8.Which number has the prime factorisation 3 × 5 × 7?
Answer: 105
- 3 × 5 × 7 = 105
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.
- Celebrate what went well first, then pick one thing to work on next.