Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 3 — Practice Set 3 — 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 3 — Practice Set 3 — Answers
Keep splitting each number into two factors until every branch ends in a prime. Write repeated factors with an index, e.g. 2 × 2 × 2 = 23.
1.Use a factor tree to write 99 as a product of prime factors in index form.
Answer: 32×11
- 99 = 3 × 33
- 33 = 3 × 11
- So 99 = 3 × 3 × 11 = 32 × 11
2.Which number has the prime factorisation 2 × 32 × 7?
Answer: 126
- 2 × 3 × 3 × 7 = 126
3.Use a factor tree to write 440 as a product of prime factors in index form.
Answer: 23×5×11
- 440 = 2 × 220
- 220 = 2 × 110
- 110 = 2 × 55
- 55 = 5 × 11
- So 440 = 2 × 2 × 2 × 5 × 11 = 23 × 5 × 11
4.Which number has the prime factorisation 2 × 32 × 5 × 7?
Answer: 630
- 2 × 3 × 3 × 5 × 7 = 630
5.Use a factor tree to write 60 as a product of prime factors in index form.
Answer: 22×3×5
- 60 = 2 × 30
- 30 = 2 × 15
- 15 = 3 × 5
- So 60 = 2 × 2 × 3 × 5 = 22 × 3 × 5
6.Which number has the prime factorisation 2 × 52 × 7?
Answer: 350
- 2 × 5 × 5 × 7 = 350
7.Use a factor tree to write 385 as a product of prime factors in index form.
Answer: 5×7×11
- 385 = 5 × 77
- 77 = 7 × 11
- So 385 = 5 × 7 × 11 = 5 × 7 × 11
8.Which number has the prime factorisation 2 × 112?
Answer: 242
- 2 × 11 × 11 = 242
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.