Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 3 — Practice Set 4 — 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 4 — 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 420 as a product of prime factors in index form.
Answer: 22×3×5×7
- 420 = 2 × 210
- 210 = 2 × 105
- 105 = 3 × 35
- 35 = 5 × 7
- So 420 = 2 × 2 × 3 × 5 × 7 = 22 × 3 × 5 × 7
2.Which number has the prime factorisation 2 × 52 × 11?
Answer: 550
- 2 × 5 × 5 × 11 = 550
3.Use a factor tree to write 330 as a product of prime factors in index form.
Answer: 2×3×5×11
- 330 = 2 × 165
- 165 = 3 × 55
- 55 = 5 × 11
- So 330 = 2 × 3 × 5 × 11 = 2 × 3 × 5 × 11
4.Which number has the prime factorisation 3 × 7 × 11?
Answer: 231
- 3 × 7 × 11 = 231
5.Use a factor tree to write 198 as a product of prime factors in index form.
Answer: 2×32×11
- 198 = 2 × 99
- 99 = 3 × 33
- 33 = 3 × 11
- So 198 = 2 × 3 × 3 × 11 = 2 × 32 × 11
6.Which number has the prime factorisation 2 × 3 × 11?
Answer: 66
- 2 × 3 × 11 = 66
7.Use a factor tree to write 275 as a product of prime factors in index form.
Answer: 52×11
- 275 = 5 × 55
- 55 = 5 × 11
- So 275 = 5 × 5 × 11 = 52 × 11
8.Which number has the prime factorisation 5 × 72?
Answer: 245
- 5 × 7 × 7 = 245
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.