• determining if a 1-digit number is a factor of a given number,

• listing all factors of a given

number up to 100,

• finding the common factors

of two given numbers

What will we learn today?

Whole Numbers Factors

A factor is a smaller number that divides exactly any larger number and gives the remainder zero.

For example,

6 is not "exactly divisible" by 4 and 5.

So, 4 and 5 are not factors of 6.

What are factors?

How to find factors of a number?

We will find all the factors of 12 by finding all the numbers that 12 can be exactly divided by.

12 is exactly divisible by 1, 2, 3, 4, 6 and 12. So 1, 2, 3, 4, 6 and 12 are the factors of 12.

12 ÷ 1 = 12 12 ÷ 2 = 6 12 ÷ 3 = 4

12 ÷ 4 = 3 12 ÷ 6 = 2 12 ÷ 12 = 1

Write all the factors for the numbers below (the first one is done for you):

4 1 2 4

7 1 7

9 1 3

15 1 15

Write all the factors for the numbers below (the first one is done for you):

4 1 2 4

7 1 7 1 x 7 = 7

9 1 3

15 1 15

Write all the factors for the numbers below (the first one is done for you):

4 1 2 4

7 1 7 1 x 7 = 7

9 1 3 9 1 x 9 = 9 , 3 x 3 = 9

15 1 15

Write all the factors for the numbers below (the first one is done for you):

4 1 2 4

7 1 7 1 x 7 = 7

9 1 3 9 1 x 9 = 9 , 3 x 3 = 9

15 1 3 5 15

1 x 15 = 15

3 x 5 = 15

What are the factors of 20?

What are the factors of 20?

1 x 20 = 20

2 x 10 = 20

4 x 5 = 20

Step 1:

Write down the multiplication sentences of 20.

What are the factors of 20?

1 x 20 = 20

2 x 10 = 20

4 x 5 = 20

Step 2: Do not write the factors twice.

4 x 5 = 5 x 4. You only need to write down 4 and 5 once.

What are the factors of 20?

1 x 20 = 20

2 x 10 = 20

4 x 5 = 20

20 is exactly divisible by 1, 2, 4, 5, 10 and 20.

So 1, 2, 4, 5, 10 and 20 are the factors of 20.

What are the common factors of 40 and 72?

What are the common factors of 40 and 72?

1 x 40 = 40

2 x 20 = 40

4 x 10 = 40

5 x 8 = 40

1 x 72 = 72 2 x 36 = 72 3 x 24 = 72 4 x 18 = 72 6 x 12 = 72 8 x 9 = 72

List down all the factors.

Step 1:

What are the common factors of 40 and 72?

1 x 40 = 40

2 x 20 = 40

4 x 10 = 40

5 x 8 = 40

1 x 72 = 72 2 x 36 = 72 3 x 24 = 72 4 x 18 = 72 6 x 12 = 72 8 x 9 = 72

Circle the common number you see.

Step 2:

What are the common factors of 40 and 72?

1 x 40 = 40

2 x 20 = 40

4 x 10 = 40

5 x 8 = 40

1 x 72 = 72 2 x 36 = 72 3 x 24 = 72 4 x 18 = 72 6 x 12 = 72 8 x 9 = 72

The common factors are 1, 2, 4 and 8.

Are you ready to try out the questions?