IMO Number Theory

Question 1

Which of the following numbers is a prime number?

Accepted Answer

29

Answer

29 is prime because it has no divisors other than 1 and itself.

Question 2

What is the LCM of 4 and 6?

Accepted Answer

12

Answer

The Least Common Multiple of 4 and 6 is 12, the smallest number both divide evenly.

Question 3

What is the HCF (GCD) of 18 and 24?

Accepted Answer

6

Answer

The Highest Common Factor of 18 and 24 is 6, as 6 is the largest number that divides both.

Question 4

Which of the following is a composite number?

Accepted Answer

15

Answer

15 = 3 × 5, so it is composite because it has factors other than 1 and itself.

Question 5

What are the prime factors of 36?

Accepted Answer

2 and 3

Answer

36 = 2² × 3², so its prime factors are 2 and 3.

IMO - International Mathematics Olympiad Practice Test