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Posts Tagged ‘whole numbers’

Is 15 a composite number? -Is an example of a math composite number problem that can be easily answered using the How to identify whole numbers that are prime or composite steps.

There are different ways to answer the question “Is 15 a composite number?” or any other Prime numbers and Composite numbers problems.

The first way to determine if 15 is a prime number of a composite number is to look at the prime number and composite number chart. The chart below show all Composite numbers from 1 to 100.

All composite number to 100

List of Composite numbers showing that 15 is a composite number.

How to identify whole numbers that are prime or composite example

Identifying whole numbers that are prime or Composite numbers is simple, just follow the How to identify whole numbers that are prime or composite steps.

Is 13 a composite number?

• Divide 13 by 2 – you will find that 13 is not divisible by 2.
• Divide 13 by 3 – you will find that 13 is not divisible by 3.
• Divide 13 by 5 – you will find that 13 is not divisible by 5.
• Divide 13 by 7 – you will find that 13 is not divisible by 7.
• Divide 13 by 11 – you will find that 13 is not divisible by 11.
• Divide 13 by 13 – you will find that 13 divided by 13 gives 1.

That means 13 is only divisible by 1 and itself. Therefore, 13 is a prime number.

Is 25 a composite number?

• Divide 25 by 2 – you will find that 25 is not divisible by 2.
• Divide 25 by 3 – you will find that 25 is not divisible by 3.
• Divide 25 by 5 – you will find that 25 divided by 5 equals 5.

That means at least 1, 5, and 25 are factors of 25. 25 is therefore not a prime number. 25 is therefore a composite number.

What is the smallest positive number?

The smallest positive number is 2.

So, the fist step of How to identify whole numbers that are prime or composite is to divide that number by 2. What do you get?

In this example, we divide 10 by 2. The answer is 5. What does this Mean? It means 10 has more than 2 factors: 1, 2, 5, and itself. Therefore, 10 is a composite number and not a prime number. For whole numbers such as 10, all you need to know to identify Prime numbers and Composite numbers is the first step of How to identify whole numbers that are prime or composite.

However, if you are faced with a whole number that the smallest whole number (2) cannot divide into, then you should move onto the second step of How to identify whole numbers that are prime or composite. For example, let’s consider 21.

How to identify whole numbers that are prime or composite Step 2

21 is clearly not divisible by 2 since dividing 21 by 2 gives 10.5 which is not a whole number.

The second step of How to identify whole numbers that are prime or composite is to divide the number (in this case 21) by the next smallest prime number. The next smallest prime number is 3, therefore, divide 21 by 3. What do you get?

Dividing 21 by 3 gives 7. That means, 21 has more than 2 factors: 1, 3, 7, and 21. That means 21 is a composite number and not a prime number.