Year 5 Prime Factorisation (Factor Trees) Worksheet — Level 3 — Practice Set 3 — Answers
Answer sheet with worked solutions for the Year 5 factors, multiples & primes worksheet.
Success TutoringWorksheetsAnswer sheetYear 5 · Mathematics · Factors, Multiples & PrimesYear 5 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 726 as a product of prime factors in index form.
Answer: 2×3×112
- 726 = 2 × 363
- 363 = 3 × 121
- 121 = 11 × 11
- So 726 = 2 × 3 × 11 × 11 = 2 × 3 × 112
2.Which number has the prime factorisation 3 × 5 × 7?
Answer: 105
- 3 × 5 × 7 = 105
3.Use a factor tree to write 396 as a product of prime factors in index form.
Answer: 22×32×11
- 396 = 2 × 198
- 198 = 2 × 99
- 99 = 3 × 33
- 33 = 3 × 11
- So 396 = 2 × 2 × 3 × 3 × 11 = 22 × 32 × 11
4.Which number has the prime factorisation 5 × 72?
Answer: 245
- 5 × 7 × 7 = 245
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 2 × 5 × 11?
Answer: 110
- 2 × 5 × 11 = 110
7.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
8.Which number has the prime factorisation 22 × 5 × 7?
Answer: 140
- 2 × 2 × 5 × 7 = 140
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.