Prime & Composite Numbers
• A prime number has only two factors, 1 and itself.
• A composite number has more than two factors.
• “1” is a special case. It is neither prime nor composite since it has only one factor, which is 1.
• “2” is the only even prime number. All other even numbers are divisible by 2, so all other even numbers are composite.
Let’s find the prime numbers from 1 – 100…
• Put a box around “1” because it is neither prime nor composite
• Circle “2.” It is the first prime number. Now cross out all multiples of 2.
• Circle “3.” It the next prime number. Cross out all multiples of 3.
• Circle “5.” It is the next prime number. Cross out all multiples of 5.
• Circle “7.” It is the next prime number. Cross out all multiples of 7.
• Highlight all numbers circled or not crossed out – these are the PRIME numbers from 1 – 100.
There should be twenty-five prime numbers.
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