GoldStudent.com - Prime Factoring 1st tutorial

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In this tutorial we will learn how to do prime factoring.

To begin let's look at the definition:

A number's prime factors are the prime numbers that multiplied together give the number.

The tools you'll need to do prime factoring are to learn a few tricks and to know the first few prime numbers.

Let's begin by learning the first few prime numbers, those less than 20:
This are 2, 3, 5, 7, 11, 13, 17 and 19.

This numbers are only divisible by them selfs or by 1. Therefore they are prime numbers.

Now let's learn some tricks:

1. A number is divisible by 2 if it is even, in other words if it ends in 2, 4, 6, 8 or 0.

2. Another trick is that a number is divisible by 3 if the sum of its digits is divisible by 3. So, for example, number 21. If you take the first digit, 2, and added at the second digit, 1, you get the result 3, that number is divisible by 3. So 21 is divisible by 3.

3. A third trick is that a number is divisible by 5 if it ends in 0 or 5. So for example 155 is divisible by 5, as is 210 but 214 is not divisible by 5.

Let's do an example:

Let's find the prime factor of the number 30.

1. First of all we notice that 30 is an even number because ends in the digit 0, therefore it's divisible by 2. We can write 30 as 2 x 15.

2. 15 is not prime. It ends in 5 so is divisible by 5: 15 is 3 x 5.

3. All our factors are prime, so we find that the answer to prime factors of the 30 are the 30 = 2 x 3 x 5.

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• math video
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• prime factoring
• calculate prime factors
• find the prime factors
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