This set of Discrete Mathematics Multiple Choice Questions & Answers (MCQs) focuses on “Primes and Greatest Common Divisors”.

1. The prime factorization of 7007 is __________

a) 7^{3}.11.13

b) 7^{2}.11.13

c) 7.11.13

d) 7.11^{3}.13

View Answer

Explanation: Perform successive division beginning with 2.

2. Out of following which one is Mersenne Primes?

a) 3

b) 7

c) 2047

d) 31

View Answer

Explanation: 2047 = 23.89 also not in form of 2

^{b}-1 form.

3. Out of the following which of these integers is not prime?

a) 21

b) 35

c) 71

d) 101

View Answer

Explanation: 35 = 5.7 which is the product of two prime numbers.

4. The prime factorization of 1001 is __________

a) 7^{3}.11.13

b) 7^{2}.11.13

c) 7.11.13

d) 7.11^{3}.13

View Answer

Explanation: Perform successive division beginning with 2.

5. Which positive integer less than 21 are relatively prime to 21?

a) 18

b) 19

c) 21

d) 24

View Answer

Explanation: gcd(19,21) = 1. According to the definition of relatively prime gcd of two numbers is 1.

6. Is 7, 8, 9, 11 are pairwise relatively prime. Is it True or False?

a) True

b) False

View Answer

Explanation: gcd(7, 9) = gcd(8, 9) = gcd(9, 11) = gcd(11, 7) = 1. The numbers 7 and 11 are prime and numbers 8 and 9 are relatively prime.

7. The greatest common divisor of 3^{13}.5^{17} and 2^{12}.3^{5} is __________

a) 3^{0}

b) 3^{1}

c) 3^{3}

d) 3^{5}

View Answer

Explanation: gcd(a, b) = 3

^{min(13, 5)}.5

^{min(17, 0)}.2

^{min(12, 0)}.

8. The greatest common divisor of 0 and 5 is ___________

a) 0

b) 1

c) 2

d) 5

View Answer

Explanation: gcd(0, 5) = 0

^{min(1, 0)}.5

^{min(0, 1)}.

9. The lcm of 3 and 21 is ________ if gcd(3,21)=3.

a) 3

b) 12

c) 21

d) 42

View Answer

Explanation: 3 * lcm(3, 21) = 63 hence, lcm(3, 21) = 63 / 3 = 21.

10. The least common multiple of 41.42 and 42.41 is ____________

a) 42

b) 41

c) 84

d) 41.42

View Answer

Explanation: lcm(41 * 42, 42 * 42) = 41.42.42.41 / 41.42 = 41.42.

**Sanfoundry Global Education & Learning Series – Discrete Mathematics**

To practice all areas of Discrete Mathematics, __here is complete set of 1000+ Multiple Choice Questions and Answers__.