Unit 12 · Class 6 IB MYP · MCQ Test
Prime Factors & Divisibility MCQ Test — Class 6 IB MYP
Practice 10 multiple-choice questions with instant answer reveal and explanations.
Prime Factors & Divisibility — MCQ Questions
1Which of these numbers is a prime number?
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Answer: 17
Hint: A prime number has exactly two factors: 1 and itself.
Solution:
Check each number:
12 = 2 × 6, so not prime
15 = 3 × 5, so not prime
17 has no factors other than 1 and 17, so it is prime
21 = 3 × 7, so not prime
2What is the smallest prime number?
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Answer: 2
Hint: Remember, 1 is NOT a prime number.
Solution:
0 is not prime (it has infinitely many factors)
1 is not prime (it has only one factor)
2 is prime — its only factors are 1 and 2
So the smallest prime number is 2
3Is 24 divisible by 3?
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Answer: Yes, because 2 + 4 = 6 which is divisible by 3
Hint: A number is divisible by 3 if the sum of its digits is divisible by 3.
Solution:
To check divisibility by 3, add the digits:
2 + 4 = 6
6 ÷ 3 = 2, so 6 is divisible by 3
Therefore 24 is divisible by 3
4List all the factors of 18.
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Answer: 1, 2, 3, 6, 9, 18
Hint: Check every number from 1 up to 18 to see if it divides 18 evenly.
Solution:
18 ÷ 1 = 18 ✓
18 ÷ 2 = 9 ✓
18 ÷ 3 = 6 ✓
18 ÷ 6 = 3 ✓ (already found)
Factors of 18: 1, 2, 3, 6, 9, 18
5Express 12 as a product of its prime factors.
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Answer: $2^2 \times 3$
Hint: Break 12 down using a factor tree until all factors are prime.
Solution:
Start with 12:
12 = 2 × 6
6 = 2 × 3
So 12 = 2 × 2 × 3 — $12 = 2^2 \times 3$
6Which of these numbers is divisible by 5?
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Answer: 85
Hint: A number is divisible by 5 if its last digit is 0 or 5.
Solution:
A number is divisible by 5 if it ends in 0 or 5
73 ends in 3 ✗
85 ends in 5 ✓
92 ends in 2 ✗
61 ends in 1 ✗
7What is the HCF (highest common factor) of 8 and 12?
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Answer: 4
Hint: List the factors of each number and find the largest one they share.
Solution:
Factors of 8: 1, 2, 4, 8
Factors of 12: 1, 2, 3, 4, 6, 12
Common factors: 1, 2, 4
The highest common factor is 4
8What is the LCM (least common multiple) of 4 and 6?
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Answer: 12
Hint: List the multiples of each number until you find the smallest one they share.
Solution:
Multiples of 4: 4, 8, 12, 16, 20, …
Multiples of 6: 6, 12, 18, 24, …
The smallest common multiple is 12
9How many prime numbers are there between 1 and 10?
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Answer: 4
Hint: Check each number: 2, 3, 4, 5, 6, 7, 8, 9.
Solution:
2 — prime ✓
3 — prime ✓
4 = 2 × 2 — not prime
5 — prime ✓
6 = 2 × 3 — not prime
7 — prime ✓
8, 9 — not prime
There are 4 primes: 2, 3, 5, 7
10Is 36 divisible by 4?
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Answer: Yes, because 36 ÷ 4 = 9
Hint: A number is divisible by 4 if the last two digits form a number divisible by 4.
Solution:
Check: 36 ÷ 4 = 9 with no remainder
So 36 is divisible by 4
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Tips for Prime Factors & Divisibility MCQs
- 1Read each question carefully and identify what is being asked before looking at the options.
- 2Try to solve the problem mentally or on paper first, then match your answer with the options.
- 3Use elimination — rule out clearly wrong options to improve your chances even when unsure.
- 4Check units, signs, and edge cases — these are common traps in Prime Factors & Divisibility MCQs.
- 5Review your mistakes after completing the test to build lasting understanding.
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