Which of the following is a group of composite numbers?
- 4, 9, 15
- 4, 5, 7
- 3, 8, 9
- None of these
Explanation
A composite number is a positive integer that has at least one positive divisor other than 1 and itself.
Let's examine the numbers:
4: divisors are 1, 2, and 4 (composite)
9: divisors are 1, 3, and 9 (composite)
15: divisors are 1, 3, 5, and 15 (composite)
Since all numbers (4, 9, 15) have divisors other than 1 and themselves, they are composite numbers.
The group 4, 9, 15 consists entirely of composite numbers.
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