Divisibility Rules for 4 and 9

Divisibility Rules for 4 and 9

How do we know if a number is divisible?

Read the slide to the right for the explanation.

Multiple Choice

What is the divisibility rule for 2?

• The number has to be even

• The number has to be odd

• The number has to end in a 0

Multiple Choice

What is the divisibility rule for 3?

• The number has to be even

• The number has to be odd

• The sum of the digits have to be a multiple of 3

Divisibility Rule for 3

The sum of the digits have to add up to a multiple of 3

Example: 3, 6, 9, 12, 15....

Multiple Choice

What is the divisibility rule for 6?

• The number has to be even

• The digits have to add up to 6

• If the number works for BOTH divisibility rules for 2 and 3, it will work for 6.

• If the number works for ONE of divisibility rules for 2 and 3, it will work for 6.

Divisibility Rule for 6

The number has to work with both 2 and 3 in divisibility rules. If it only works for one of them, it will not work for 6.

Open Ended

Make a prediction. What do you think the divisibility rule for 4 will be? Think about the other rules we have already reviewed.

Multiple Choice

After watching the video, what is the divisibility for 4?

• If you double the number and it equals four, it is divisible by four

• The last two digits of the number are divisible by four

• If you add the last two digits, it will be divisible by four.

Multiple Choice

After watching the video, what is the divisibility for 9?

• If you double the number and it equals nine, it is divisible by nine

• The last two digits of the number are divisible by nine

• If you add the last two digits and the number is a multiple of 9.

Multiple Select

Select two of the numbers that are divisible by 4.

• 14

• 28

• 33

• 40

Multiple Select

Select two of the numbers that are divisible by 9.

• 9

• 17

• 34

• 45

Multiple Select

Select the of the number that is divisible by 4 and 9.

• 13

• 24

• 36

• 49

Review of Divisibility Rules for 4 and 9

• Any number that is divisible by 4 has to have the final two digits of the number be able to be divided by 4

• Examples for 4 that work: 16, 24, 32, 40

• Any number that is divisible by 9 has to be the SUM of the digits as a multiple of 9

• Example: 27 -> 2 + 7 = 9, 54 -> 5 + 4 = 9