To determine if 90 is a prime number or a composite number, we simply look at the factors for 90.
If the factors of 90 are only 90 and 1, then we know that 90 is a prime number. Otherwise, 90 is a composite number.
To explain better, if 90 is only divisible by 1 and 90, then it is a prime number, and if 90 is divisible by more than 90 and 1, then it is a composite number.
The factors of 90 are as follows:
1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
Therefore, since 90 is divisible by more than one and itself, the answer to the
question "Is 90 prime or composite?" is highlighted in blue below.
composite
Is 91 prime or composite?
OK. Now you know that 90 is a composite number. Use our logic above and see if
you can figure out if the next number on our list is prime or composite before you check your answer.
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