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 770 as a product of prime factors in index form.
Answer: 2×5×7×11
- 770 = 2 × 385
- 385 = 5 × 77
- 77 = 7 × 11
- So 770 = 2 × 5 × 7 × 11 = 2 × 5 × 7 × 11
2.Which number has the prime factorisation 22 × 5 × 11?
Answer: 220
- 2 × 2 × 5 × 11 = 220
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 22 × 32 × 52?
Answer: 900
- 2 × 2 × 3 × 3 × 5 × 5 = 900
5.Use a factor tree to write 525 as a product of prime factors in index form.
Answer: 3×52×7
- 525 = 3 × 175
- 175 = 5 × 35
- 35 = 5 × 7
- So 525 = 3 × 5 × 5 × 7 = 3 × 52 × 7
6.Which number has the prime factorisation 5 × 72?
Answer: 245
- 5 × 7 × 7 = 245
7.Use a factor tree to write 924 as a product of prime factors in index form.
Answer: 22×3×7×11
- 924 = 2 × 462
- 462 = 2 × 231
- 231 = 3 × 77
- 77 = 7 × 11
- So 924 = 2 × 2 × 3 × 7 × 11 = 22 × 3 × 7 × 11
8.Which number has the prime factorisation 2 × 3 × 11?
Answer: 66
- 2 × 3 × 11 = 66
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.