Question

put a check by all the prime numbers.
2
3
13
17
20
21
none of the above

Explanation:

Step1: Recall prime number definition

A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

Step2: Check each number

• For 2: Divisors are 1 and 2. Prime.
• For 3: Divisors are 1 and 3. Prime.
• For 13: Divisors are 1 and 13. Prime.
• For 17: Divisors are 1 and 17. Prime.
• For 20: Divisors include 1, 2, 4, 5, 10, 20. Not prime.
• For 21: Divisors include 1, 3, 7, 21. Not prime.

Answer:

The prime numbers are 2, 3, 13, 17. So the boxes to check are:

• $\square$ 2 (check this box)
• $\square$ 3 (check this box)
• $\square$ 13 (check this box)
• $\square$ 17 (check this box)
• $\square$ 20 (do not check)
• $\square$ 21 (do not check)
• $\square$ None of the above (do not check)