Prime Time — Practice

Q1. Of Ganita Prakash, a prime number is a number that has

• A. Exactly one factor
• B. Exactly two factors — 1 and itself
• C. More than two factors
• D. Only even factors

Q2. Which of the following lists the first few prime numbers of Ganita Prakash?

• A. 1, 2, 3, 5, 7, 11, 13
• B. 2, 3, 5, 7, 11, 13, 17, 19
• C. 2, 4, 6, 8, 10, 12, 14
• D. 3, 5, 7, 9, 11, 13, 15

Q3. Numbers that have more than two factors are called

• A. Co-prime numbers
• B. Twin primes
• C. Composite numbers
• D. Perfect numbers

Q4. What is said about the number 1?

• A. It is the smallest prime number
• B. It is a composite number
• C. It is neither prime nor composite
• D. It is both prime and composite

Q5. Which is the only even prime number?

• A. 0
• B. 1
• C. 2
• D. 4

Q6. In the Jump Jackpot game, the numbers 1, 2, 3, 4, 6, 8, 12 and 24 all divide 24 exactly. Such numbers are called

• A. Multiples of 24
• B. Factors or divisors of 24
• C. Primes of 24
• D. Common multiples of 24

Q7. Which list correctly gives all the factors of 24 as shown in the Jump Jackpot game?

• A. 1, 2, 3, 4, 6, 12
• B. 1, 2, 3, 4, 6, 8, 12, 24
• C. 2, 3, 4, 6, 8, 12
• D. 1, 24, 48, 72

Q8. On, the factors of 14 are listed as

• A. 1, 2, 7, 14
• B. 1, 7, 14
• C. 2, 7, 14
• D. 1, 2, 7

Q9. From the Jump Jackpot example the common factors of 14 and 36 are

• A. 1 and 7
• B. 1 and 2
• C. 2 and 7
• D. 1, 2 and 7

Q10. In the idli-vada game which is the first number for which the players should say 'idli-vada'?

• A. 5
• B. 10
• C. 15
• D. 30

Q11. In the idli-vada game, a player must say 'idli' instead of the number for multiples of

• A. 3
• B. 5
• C. 7
• D. Both 3 and 5

Q12. The method of Ganita Prakash for listing all prime numbers up to 100 by crossing out multiples is called

• A. Euclid's algorithm
• B. Sieve of Eratosthenes
• C. Sieve of Pythagoras
• D. Goldbach's method

Q13. Two numbers are said to be co-prime if they have

• A. Exactly two common factors
• B. No common factor other than 1
• C. At least one common prime factor
• D. The same number of factors

Q14. Writing a composite number as a product of only prime numbers is called its

• A. Co-prime factorisation
• B. Common factorisation
• C. Prime factorisation
• D. Multiple factorisation

Q15. The prime factorisation of 56 is

• A. 2 × 2 × 14
• B. 4 × 14
• C. 2 × 2 × 2 × 7
• D. 7 × 8