Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 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 — 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 990 as a product of prime factors in index form.
Answer: 2×32×5×11
- 990 = 2 × 495
- 495 = 3 × 165
- 165 = 3 × 55
- 55 = 5 × 11
- So 990 = 2 × 3 × 3 × 5 × 11 = 2 × 32 × 5 × 11
2.Which number has the prime factorisation 2 × 5 × 7?
Answer: 70
- 2 × 5 × 7 = 70
3.Use a factor tree to write 147 as a product of prime factors in index form.
Answer: 3×72
- 147 = 3 × 49
- 49 = 7 × 7
- So 147 = 3 × 7 × 7 = 3 × 72
4.Which number has the prime factorisation 2 × 32 × 11?
Answer: 198
- 2 × 3 × 3 × 11 = 198
5.Use a factor tree to write 882 as a product of prime factors in index form.
Answer: 2×32×72
- 882 = 2 × 441
- 441 = 3 × 147
- 147 = 3 × 49
- 49 = 7 × 7
- So 882 = 2 × 3 × 3 × 7 × 7 = 2 × 32 × 72
6.Which number has the prime factorisation 2 × 32 × 5?
Answer: 90
- 2 × 3 × 3 × 5 = 90
7.Use a factor tree to write 441 as a product of prime factors in index form.
Answer: 32×72
- 441 = 3 × 147
- 147 = 3 × 49
- 49 = 7 × 7
- So 441 = 3 × 3 × 7 × 7 = 32 × 72
8.Which number has the prime factorisation 22 × 3 × 5?
Answer: 60
- 2 × 2 × 3 × 5 = 60
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.