Math Worksheets

Archive for September, 2008

Prime factors are factors of another number that are Prime numbers.

What is a prime factor?

Prime factors are Prime numbers that are factors of an integer.

Finding prime factor

Finding prime factor is easy. Take a number and divide it by the smallest Prime numbers you know. An example of how to find prime factors is shown below.

What are prime factors of 25?

Step 1: Divide 25 by the smallest prime number you know. The smallest prime number you know is 2.

So, divide 25 by 2.

25 ÷ 2 = 12.5, not an integer (whole number), therefore the prime number 2 is not a prime factor of 25.

Step 2: Divide 25 by the NEXT smallest prime number you know. The NEXT smallest prime number you know is 3.

So, divide 25 by 3.

25 ÷ 3 = 8.3 recurring, not an integer (whole number), therefore the prime number 3 is not a prime factor of 25.

Step 3: Divide 25 by the NEXT smallest prime number you know. The NEXT smallest prime number you know is 5.

So, divide 25 by 5.

25 ÷ 5 = 5, an integer (whole number), therefore the prime number 5 is a prime factor of 25.

Step 4: Divide the remaining number by the same prime number (5 in this case) or the next smallest prime number you know (7).

Since the remaining number is 5, so divide 5 by 5.

5 ÷ 5 = 1.

Stop the process when the remainder of the divisions is 1.

That means, 25 has only one prime factor, 5.

Back to Prime numbers page

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