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 686 as a product of prime factors in index form.
Answer: 2×73
- 686 = 2 × 343
- 343 = 7 × 49
- 49 = 7 × 7
- So 686 = 2 × 7 × 7 × 7 = 2 × 73
2.Which number has the prime factorisation 3 × 5 × 72?
Answer: 735
- 3 × 5 × 7 × 7 = 735
3.Use a factor tree to write 980 as a product of prime factors in index form.
Answer: 22×5×72
- 980 = 2 × 490
- 490 = 2 × 245
- 245 = 5 × 49
- 49 = 7 × 7
- So 980 = 2 × 2 × 5 × 7 × 7 = 22 × 5 × 72
4.Which number has the prime factorisation 2 × 32 × 72?
Answer: 882
- 2 × 3 × 3 × 7 × 7 = 882
5.Use a factor tree to write 350 as a product of prime factors in index form.
Answer: 2×52×7
- 350 = 2 × 175
- 175 = 5 × 35
- 35 = 5 × 7
- So 350 = 2 × 5 × 5 × 7 = 2 × 52 × 7
6.Which number has the prime factorisation 3 × 5 × 11?
Answer: 165
- 3 × 5 × 11 = 165
7.Use a factor tree to write 825 as a product of prime factors in index form.
Answer: 3×52×11
- 825 = 3 × 275
- 275 = 5 × 55
- 55 = 5 × 11
- So 825 = 3 × 5 × 5 × 11 = 3 × 52 × 11
8.Which number has the prime factorisation 5 × 7 × 11?
Answer: 385
- 5 × 7 × 11 = 385
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.