Common factors & common multiples

Find common factors and common multiples (HCF and LCM) of two or more numbers

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1
What is a common factor of 6 and 8? A) 2 B) 3 C) 4 D) 5
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2
Find the lowest common multiple (LCM) of 4 and 6. LCM of 4 and 6 = ___
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3
Is this statement true or false? 6 is a common factor of 12 and 18. A) True B) False
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4
Which number is a common multiple of 3 and 5? A) 8 B) 10 C) 15 D) 20
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5
Find the highest common factor (HCF) of 12 and 18. HCF of 12 and 18 = ___
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6
Match each pair of numbers to their HCF. Match each item on the left to one on the right. Left: 8 and 12, 9 and 15, 10 and 25, 14 and 21 Right: 4, 3, 5, 7
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7
What is the LCM of 6 and 8? A) 12 B) 14 C) 24 D) 48
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8
Find the HCF of 24 and 36. HCF of 24 and 36 = ___
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9
What is the LCM of 5 and 12? A) 17 B) 30 C) 60 D) 120
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10
Is this statement true or false? The HCF of 7 and 11 is 1. A) True B) False
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Answer key

Common factors & common multiples · for parents and teachers

1
2
Factors of 6: 1, 2, 3, 6. Factors of 8: 1, 2, 4, 8. The common factors are 1 and 2.
2
12
Multiples of 4: 4, 8, 12, 16... Multiples of 6: 6, 12, 18... The lowest common is 12.
3
True
12 ÷ 6 = 2 and 18 ÷ 6 = 3, so 6 is a common factor.
4
15
15 = 3 × 5 = 5 × 3, so 15 is in both the 3 and 5 times tables.
5
6
Common factors of 12 and 18 are 1, 2, 3 and 6. The highest is 6.
6
8 and 12 → 4; 9 and 15 → 3; 10 and 25 → 5; 14 and 21 → 7
HCF(8,12) = 4. HCF(9,15) = 3. HCF(10,25) = 5. HCF(14,21) = 7.
7
24
Multiples of 6: 6, 12, 18, 24. Multiples of 8: 8, 16, 24. LCM is 24.
8
12
Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24. Factors of 36: 1, 2, 3, 4, 6, 9, 12, 18, 36. Common: 1, 2, 3, 4, 6, 12. HCF is 12.
9
60
5 and 12 have no common factor except 1, so LCM = 5 × 12 = 60.
10
True
7 and 11 are both prime, so their only common factor is 1.