Chapter 7: Numbers — Online MCQ Test
MATHS · Samacheer Kalvi 6th · Tamil Nadu State Board
Practice Chapter 7: Numbers with a free chapter-wise online MCQ test.
This chapter covers: Prime numbers, Composite numbers, Divisibility rules, HCF, LCM.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter 7: Numbers — Important Questions & Answers
Which of the following is a prime number?
- A. 4
- B. 7
- C. 9
- D. 10
Answer: B. 7
7 is a prime number because it has exactly two factors: 1 and 7. All other options have more than two factors.
7 is a prime number because it has exactly two factors: 1 and 7. All other options have more than two factors.
A composite number is a natural number that has _____ factors.
- A. exactly one
- B. exactly two
- C. more than two
- D. no
Answer: C. more than two
A composite number is defined as a natural number with more than two factors. Numbers like 4, 6, 8, 9, etc. are composite.
A composite number is defined as a natural number with more than two factors. Numbers like 4, 6, 8, 9, etc. are composite.
Is 1 a prime number or a composite number?
- A. Prime number
- B. Composite number
- C. Neither prime nor composite
- D. Both prime and composite
Answer: C. Neither prime nor composite
1 is neither prime nor composite because a prime number must have exactly two distinct factors, and 1 only has one factor (itself).
1 is neither prime nor composite because a prime number must have exactly two distinct factors, and 1 only has one factor (itself).
Which number is NOT a factor of 24?
- A. 6
- B. 8
- C. 7
- D. 4
Answer: C. 7
7 does not divide 24 evenly. The factors of 24 are: 1, 2, 3, 4, 6, 8, 12, and 24.
7 does not divide 24 evenly. The factors of 24 are: 1, 2, 3, 4, 6, 8, 12, and 24.
What is the HCF of 12 and 18?
- A. 3
- B. 6
- C. 9
- D. 12
Answer: B. 6
The factors of 12 are 1, 2, 3, 4, 6, 12 and factors of 18 are 1, 2, 3, 6, 9, 18. The highest common factor is 6.
The factors of 12 are 1, 2, 3, 4, 6, 12 and factors of 18 are 1, 2, 3, 6, 9, 18. The highest common factor is 6.
What is the LCM of 4 and 6?
- A. 12
- B. 24
- C. 8
- D. 10
Answer: A. 12
LCM (Least Common Multiple) is the smallest number that is a multiple of both 4 and 6. Multiples of 4: 4, 8, 12... Multiples of 6: 6, 12... The LCM is 12.
LCM (Least Common Multiple) is the smallest number that is a multiple of both 4 and 6. Multiples of 4: 4, 8, 12... Multiples of 6: 6, 12... The LCM is 12.
If HCF(a, b) = 5 and LCM(a, b) = 60, what is the relationship between them?
- A. a × b = 5 × 60 = 300
- B. a + b = 65
- C. a - b = 55
- D. a ÷ b = 12
Answer: A. a × b = 5 × 60 = 300
There is a fundamental property: For any two numbers a and b, HCF(a,b) × LCM(a,b) = a × b. So a × b = 5 × 60 = 300.
There is a fundamental property: For any two numbers a and b, HCF(a,b) × LCM(a,b) = a × b. So a × b = 5 × 60 = 300.
Which number is both prime and even?
- A. 4
- B. 2
- C. 6
- D. 8
Answer: B. 2
2 is the only even prime number because it has exactly two factors: 1 and 2. All other even numbers are divisible by 2 and have additional factors.
2 is the only even prime number because it has exactly two factors: 1 and 2. All other even numbers are divisible by 2 and have additional factors.
If a number is divisible by both 4 and 9, by which of the following must it definitely be divisible?
- A. 16
- B. 36
- C. 18
- D. 72
Answer: B. 36
If a number is divisible by both 4 and 9 (which are co-prime), it must be divisible by their product: 4 × 9 = 36. All other options don't necessarily follow.
If a number is divisible by both 4 and 9 (which are co-prime), it must be divisible by their product: 4 × 9 = 36. All other options don't necessarily follow.
The HCF and LCM of two numbers are 6 and 90 respectively. If one number is 18, what is the other number?
- A. 30
- B. 20
- C. 15
- D. 36
Answer: A. 30
Using HCF(a,b) × LCM(a,b) = a × b: 6 × 90 = 18 × b, so 540 = 18b, therefore b = 30. Verification: HCF(18, 30) = 6 ✓ and LCM(18, 30) = 90 ✓
Using HCF(a,b) × LCM(a,b) = a × b: 6 × 90 = 18 × b, so 540 = 18b, therefore b = 30. Verification: HCF(18, 30) = 6 ✓ and LCM(18, 30) = 90 ✓