Let’s solve each problem step by step. We’re finding the
prime factors of each number — that means breaking the number down into only prime numbers multiplied together.
We’ll use factor trees to help us, and then write the final answer as a multiplication of three primes (since all these numbers break into exactly three prime factors).
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Problem 1: 20
Start with 20.
Break it into two factors:
→ 20 = 4 × 5
But 4 is not prime → break 4 into 2 × 2
So: 20 = 2 × 2 × 5
✔ All are prime!
Check: 2 × 2 = 4; 4 × 5 = 20 ✔️
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Problem 2: 99
Start with 99.
Break it into two factors:
→ 99 = 9 × 11
9 is not prime → break 9 into 3 × 3
So: 99 = 3 × 3 × 11
✔ All are prime!
Check: 3 × 3 = 9; 9 × 11 = 99 ✔️
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Problem 3: 45
Start with 45.
Break it into two factors:
→ 45 = 9 × 5
9 is not prime → break 9 into 3 × 3
So: 45 = 3 × 3 × 5
✔ All are prime!
Check: 3 × 3 = 9; 9 × 5 = 45 ✔️
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Problem 4: 28
Start with 28.
Break it into two factors:
→ 28 = 4 × 7
4 is not prime → break 4 into 2 × 2
So: 28 = 2 × 2 × 7
✔ All are prime!
Check: 2 × 2 = 4; 4 × 7 = 28 ✔️
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Problem 5: 52
Start with 52.
Break it into two factors:
→ 52 = 4 × 13
4 is not prime → break 4 into 2 × 2
So: 52 = 2 × 2 × 13
✔ All are prime!
Check: 2 × 2 = 4; 4 × 13 = 52 ✔️
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Problem 6: 30
Start with 30.
Break it into two factors:
→ 30 = 6 × 5
6 is not prime → break 6 into 2 × 3
So: 30 = 2 × 3 × 5
✔ All are prime!
Check: 2 × 3 = 6; 6 × 5 = 30 ✔️
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Final Answer:
1) 2 × 2 × 5 = 20
2) 3 × 3 × 11 = 99
3) 3 × 3 × 5 = 45
4) 2 × 2 × 7 = 28
5) 2 × 2 × 13 = 52
6) 2 × 3 × 5 = 30
Parent Tip: Review the logic above to help your child master the concept of factors worksheet grade 4.
