IXL | Prime or composite | 6th grade math

Which number is prime?

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question

Which number is prime?

key idea

The only factors of a prime number are 1 and itself.
The number 1 is neither prime nor composite.

solution

The factors of 12 are 1, 2, 3, 4, 6, and 12. Since 12 has more factors than just 1 and itself, 12 is not prime.

The factors of 15 are 1, 3, 5, and 15. Since 15 has more factors than just 1 and itself, 15 is not prime.

The factors of 17 are 1 and 17. Since the only factors of 17 are 1 and itself, 17 is prime.

The only factor of 1 is 1. 1 is special because it is neither prime nor composite. So, 1 is not prime.

The prime number is 17.

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Lesson: Prime and composite numbers

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Lesson: Prime and composite numbers

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