Question 1: List all prime numbers between 1 and 20.

Answer: 2, 3, 5, 7, 11, 13, 17, 19

Question 2: Calculate whether 49 is a prime number. Show your reasoning.

Answer: 49 is not prime because it is divisible by 7.

Question 3: Determine if 73 is prime and justify your answer.

Answer: 73 is prime because it has no divisors other than 1 and itself.

Question 4: Identify the common mistake: Is 51 prime? Explain and correct the error.

Answer: 51 is not prime because it is divisible by 3. Common mistake: assuming numbers ending with 1 or 5 are prime.

Question 5: Construct a list of all prime numbers less than 30.

Answer: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29

Question 6: Plot the points corresponding to prime numbers 2, 3, 5, 7 on the number line.

Answer: Students plot points at 2, 3, 5, 7 on the grid.

Question 7: Identify which of the following are prime: 15, 17, 20, 23.

Answer: 17 and 23

Question 8: Explain why 97 is a prime number and describe how you verified this.

Answer: 97 is prime because it has no divisors other than 1 and itself. Verification involved checking divisibility by all primes less than √97 (which are 2, 3, 5, 7).

Question 9: Find the smallest prime number greater than 50.

Answer: 53

Question 10: A student claims that 91 is prime. Check this statement and correct it if necessary.

Answer: 91 is not prime because it is divisible by 7 and 13.

Question 11: Challenge: Find all prime numbers between 90 and 100. Explain your approach.

Answer: Prime numbers between 90 and 100 are 97 only. Approach: test divisibility by primes less than √100 (2, 3, 5, 7).