Year 7 Prime Factorisation (Factor Trees) Worksheet — Level 2 — 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 2 — Practice Set 3 — Answers
Keep splitting each number into two factors until every branch ends in a prime. Write the primes from smallest to largest.
1.Use a factor tree to write 180 as a product of prime factors.
Answer: 2×2×3×3×5
- 180 = 2 × 90
- 90 = 2 × 45
- 45 = 3 × 15
- 15 = 3 × 5
- So 180 = 2 × 2 × 3 × 3 × 5 = 22 × 32 × 5
2.Use a factor tree to write 225 as a product of prime factors.
Answer: 3×3×5×5
- 225 = 3 × 75
- 75 = 3 × 25
- 25 = 5 × 5
- So 225 = 3 × 3 × 5 × 5 = 32 × 52
3.Use a factor tree to write 75 as a product of prime factors.
Answer: 3×5×5
- 75 = 3 × 25
- 25 = 5 × 5
- So 75 = 3 × 5 × 5 = 3 × 52
4.Which number has the prime factorisation 2 × 3 × 7?
Answer: 42
- 2 × 3 × 7 = 42
5.Use a factor tree to write 70 as a product of prime factors.
Answer: 2×5×7
- 70 = 2 × 35
- 35 = 5 × 7
- So 70 = 2 × 5 × 7
6.Use a factor tree to write 150 as a product of prime factors.
Answer: 2×3×5×5
- 150 = 2 × 75
- 75 = 3 × 25
- 25 = 5 × 5
- So 150 = 2 × 3 × 5 × 5 = 2 × 3 × 52
7.Use a factor tree to write 245 as a product of prime factors.
Answer: 5×7×7
- 245 = 5 × 49
- 49 = 7 × 7
- So 245 = 5 × 7 × 7 = 5 × 72
8.Which number has the prime factorisation 22 × 32?
Answer: 36
- 2 × 2 × 3 × 3 = 36
Marking tips
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