10 questions · Form 1 Mathematics Bab 2: Factors and Multiples
What is the sum of all prime factors of 42?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. What is the sum of all prime factors of 42?
Answer: A
Prime factors of 42 = 2, 3, 7. Sum = 2 + 3 + 7 = 12.
2. Which of the following statements is FALSE?
Answer: A
1 is neither a prime nor a composite number because it only has one factor.
3. Which of the following is a common multiple of 4 and 6?
Answer: A
Multiples of 4: 4, 8, 12, 16, 20, 24... Multiples of 6: 6, 12, 18, 24... 24 is a common multiple.
4. Teacher Sarah wants to pack 24 pencils and 36 erasers into bags such that each bag has the same number of pencils and erasers with none left over. What is the maximum number of bags she can prepare?
Answer: A
Find the HCF of 24 and 36. HCF(24, 36) = 12.
5. Find the Lowest Common Multiple (LCM) of 6 and 8.
Answer: A
Multiples of 6: 6, 12, 18, 24... Multiples of 8: 8, 16, 24... The smallest common multiple is 24.
6. What are all the prime factors of 30?
Answer: A
30 = 2 × 3 × 5. Note that 1 is not a prime number.
7. Find the Highest Common Factor (HCF) of 16, 24, and 32.
Answer: A
Using repeated division: 16 ÷ 8 = 2, 24 ÷ 8 = 3, 32 ÷ 8 = 4. Since 2, 3, 4 share no common factors, HCF = 8.
8. Find the smallest whole number that is completely divisible by 8, 12, and 16.
Answer: A
This requires finding the LCM of 8, 12, and 16, which is 48.
9. Determine the Lowest Common Multiple (LCM) of 3, 5, and 6.
Answer: A
Using repeated division or listing, the smallest number divisible by 3, 5, and 6 is 30.
10. Which number is both a factor of 45 and a multiple of 5?
Answer: A
15 divides 45 completely (45 ÷ 15 = 3) and is a multiple of 5 (5 × 3 = 15).