Question 1

Which of the following is the smallest prime number?

Accepted Answer

The correct answer is 2. Explanation: A prime number is a natural number greater than 1 that has exactly two factors: 1 and the number itself. The smallest natural numbers are 1, 2, 3, 4... 1 is neither prime nor composite. 2 is the smallest prime number (and also the only even prime number).

Question 2

Which number is a factor of every natural number?

Accepted Answer

The correct answer is 1. Explanation: 1 divides every natural number exactly without leaving a remainder. Therefore, 1 is a factor of every natural number.

Question 3

Which of the following pairs of numbers are co-prime?

Accepted Answer

The correct answer is 4 and 15. Explanation: Two numbers are co-prime if their Highest Common Factor (HCF) is 1. Factors of 4 = 1, 2, 4 Factors of 15 = 1, 3, 5, 15 Common factor = 1. Hence, HCF = 1. Thus, 4 and 15 are co-prime.

Question 4

What is the smallest composite number?

Accepted Answer

The correct answer is 4. Explanation: A composite number has more than two factors. 1 is neither prime nor composite. 2 and 3 are prime numbers. 4 has factors 1, 2, and 4 (more than 2 factors). Thus, 4 is the smallest composite number.

Question 5

Which of the following numbers is divisible by 3?

Accepted Answer

The correct answer is 243. Explanation: A number is divisible by 3 if the sum of its digits is divisible by 3. For 243: Sum of digits = $2 + 4 + 3 = 9$. Since 9 is divisible by 3, 243 is divisible by 3.

Playing with Numbers