NCERT CLASS 6 | MATHEMATICS | GANITA PRAKASH
Chapter 5: Prime Time MCQs
1. In the Idli-Vada game, which numbers are replaced by the word ‘idli’?
A. Multiples of 2
B. Multiples of 3
C. Multiples of 4
D. Multiples of 5
Answer: B. Multiples of 3
2. In the Idli-Vada game, which numbers are replaced by the word ‘vada’?
A. Multiples of 2
B. Multiples of 3
C. Multiples of 5
D. Multiples of 10
Answer: C. Multiples of 5
3. What should players say when a number is a multiple of both 3 and 5?
A. Idli
B. Vada
C. Idli-Vada
D. Both numbers
Answer: C. Idli-Vada
4. What is the first number for which players say ‘idli-vada’ in the game using 3 and 5?
A. 10
B. 12
C. 15
D. 20
Answer: C. 15
5. Which of the following is a common multiple of 3 and 5?
A. 12
B. 18
C. 25
D. 30
Answer: D. 30
6. Which of the following is a factor of 24?
A. 5
B. 7
C. 8
D. 10
Answer: C. 8
7. Which of the following lists contains all the factors of 14?
A. 1, 2, 7, 14
B. 1, 3, 7, 14
C. 2, 4, 7, 14
D. 1, 2, 6, 14
Answer: A. 1, 2, 7, 14
8. What are common factors of two numbers?
A. Factors found in only one number
B. Factors shared by both numbers
C. Multiples of both numbers
D. Prime numbers only
Answer: B. Factors shared by both numbers
9. Which of the following is a common factor of 14 and 36?
A. 3
B. 5
C. 7
D. 2
Answer: D. 2
10. Which jump sizes will allow Jumpy to reach both 14 and 36?
A. 3 and 7
B. 1 and 2
C. 4 and 7
D. 6 and 9
Answer: B. 1 and 2
11. A number having exactly two factors is called a:
A. Composite number
B. Perfect number
C. Prime number
D. Common multiple
Answer: C. Prime number
12. Which of the following is a prime number?
A. 9
B. 12
C. 15
D. 13
Answer: D. 13
13. Which of the following is a composite number?
A. 2
B. 5
C. 7
D. 9
Answer: D. 9
14. How many factors does a prime number have?
A. One
B. Two
C. Three
D. Four
Answer: B. Two
15. Which statement about the number 1 is correct?
A. It is a prime number
B. It is a composite number
C. It is neither prime nor composite
D. It has exactly two factors
Answer: C. It is neither prime nor composite
16. What is the only even prime number?
A. 1
B. 2
C. 4
D. 6
Answer: B. 2
17. Which method is used to find prime numbers by crossing out multiples?
A. Division method
B. Sieve of Eratosthenes
C. Multiplication method
D. Factor tree method
Answer: B. Sieve of Eratosthenes
18. Who developed the method known as the Sieve of Eratosthenes?
A. Euclid
B. Aryabhata
C. Eratosthenes
D. Pythagoras
Answer: C. Eratosthenes
19. Which of the following numbers is prime?
A. 21
B. 23
C. 25
D. 27
Answer: B. 23
20. What are twin primes?
A. Two prime numbers with a difference of 1
B. Two prime numbers with a difference of 2
C. Two composite numbers with a difference of 2
D. Two numbers having the same factors
Answer: B. Two prime numbers with a difference of 2
21. Which of the following is a pair of twin primes?
A. 9 and 11
B. 15 and 17
C. 17 and 19
D. 21 and 23
Answer: C. 17 and 19
22. Two numbers are called co-prime if:
A. Both are prime numbers
B. They have no common factor other than 1
C. They have the same factors
D. Both are even numbers
Answer: B. They have no common factor other than 1
23. Which of the following pairs is co-prime?
A. 12 and 18
B. 15 and 25
C. 4 and 9
D. 20 and 30
Answer: C. 4 and 9
24. Which of the following pairs is NOT co-prime?
A. 4 and 9
B. 15 and 37
C. 18 and 35
D. 15 and 39
Answer: D. 15 and 39
25. What is the only common factor of two co-prime numbers?
A. 2
B. 3
C. 5
D. 1
Answer: D. 1
26. If two numbers are co-prime, their first common multiple is equal to:
A. Their sum
B. Their difference
C. Their product
D. Their quotient
Answer: C. Their product
27. What is prime factorisation?
A. Writing a number as a sum of prime numbers
B. Writing a number as a product of prime numbers
C. Dividing a number by 1
D. Finding all multiples of a number
Answer: B. Writing a number as a product of prime numbers
28. What is the prime factorisation of 56?
A. 2 × 2 × 2 × 7
B. 2 × 4 × 7
C. 7 × 8
D. 2 × 2 × 14
Answer: A. 2 × 2 × 2 × 7
29. Which of the following is the prime factorisation of 36?
A. 2 × 2 × 3 × 3
B. 4 × 9
C. 6 × 6
D. 2 × 18
Answer: A. 2 × 2 × 3 × 3
30. Every number greater than 1 can be written as:
A. A sum of even numbers
B. A product of prime numbers
C. A product of composite numbers only
D. A sum of prime numbers only
Answer: B. A product of prime numbers
31. Which statement about prime factorisation is correct?
A. Every number has many different prime factorisations
B. Prime factorisation is unique except for the order of factors
C. Only even numbers have prime factorisations
D. The number 1 has a prime factorisation
Answer: B. Prime factorisation is unique except for the order of factors
32. What is the prime factorisation of 105?
A. 3 × 5 × 7
B. 5 × 5 × 7
C. 3 × 7 × 7
D. 2 × 3 × 5
Answer: A. 3 × 5 × 7
33. What is the prime factorisation of 1000?
A. 2 × 2 × 5 × 5
B. 2 × 2 × 2 × 5 × 5 × 5
C. 2 × 5 × 5
D. 2 × 2 × 2 × 2 × 5
Answer: B. 2 × 2 × 2 × 5 × 5 × 5
34. Which prime factor is common to both 56 and 63?
A. 2
B. 3
C. 5
D. 7
Answer: D. 7
35. If two numbers have no common prime factor, then they are:
A. Composite
B. Co-prime
C. Equal
D. Multiples of each other
Answer: B. Co-prime
36. A number is divisible by another number if:
A. Their sum is zero
B. The remainder is zero when divided
C. Their difference is one
D. Both numbers are prime
Answer: B. The remainder is zero when divided
37. A number is divisible by 10 if its last digit is:
A. 5
B. 2
C. 0
D. 8
Answer: C. 0
38. A number is divisible by 5 if its last digit is:
A. 1 or 2
B. 0 or 5
C. 2 or 4
D. 3 or 6
Answer: B. 0 or 5
39. Which of the following numbers is divisible by 2?
A. 135
B. 247
C. 682
D. 795
Answer: C. 682
40. A number is divisible by 2 if its last digit is:
A. 1, 3, 5, 7 or 9
B. 0, 2, 4, 6 or 8
C. 2, 3, 5 or 7
D. 0 or 5
Answer: B. 0, 2, 4, 6 or 8
41. To check whether a number is divisible by 4, we need to examine:
A. Only its first digit
B. Only its last digit
C. The last two digits
D. The sum of all its digits
Answer: C. The last two digits
42. Which of the following numbers is divisible by 4?
A. 122
B. 134
C. 136
D. 142
Answer: C. 136
43. To check whether a number is divisible by 8, we examine:
A. Its first three digits
B. Its last two digits
C. Its last three digits
D. Its units digit only
Answer: C. Its last three digits
44. Which of the following numbers is divisible by 8?
A. 122
B. 128
C. 134
D. 142
Answer: B. 128
45. A leap year is generally a year that is a multiple of:
A. 2
B. 3
C. 4
D. 5
Answer: C. 4
46. Which of the following years is a leap year?
A. 2021
B. 2022
C. 2023
D. 2024
Answer: D. 2024
47. Which number in the given box (9, 16, 25, 43) is the only prime number?
A. 9
B. 16
C. 25
D. 43
Answer: D. 43
48. In the prime puzzle, what must be filled in each grid cell?
A. Composite numbers only
B. Prime numbers only
C. Even numbers only
D. Multiples of 10 only
Answer: B. Prime numbers only
49. Which of the following is a perfect number?
A. 4
B. 6
C. 8
D. 10
Answer: B. 6
50. Which pair of numbers has a product of 10,000, with neither number having 0 as its units digit?
A. 10 and 1000
B. 20 and 500
C. 16 and 625
D. 25 and 400
Answer: C. 16 and 625
