Divisibility Rules

Divisibility Rules

1, 2, 5, and 10

1s

Any number divided by 1 is that number!

Multiple Choice

 $5\div1$  

• 1

• 6

• 4

• 5

Multiple Choice

 $\frac{7}{1}$  

• 6

• 1

• 7

• 8

Multiple Choice

 $-3\div1$  

• 3

• 2

• -3

• 1

A number is divisible by 2 if...

• The number is EVEN

• Ends in 0, 2, 4, 6, 8

Multiple Choice

Is this number divisible by 2?

14

• Yes

• No

Multiple Choice

Is this number divisible by 2?

23

• Yes

• No

Multiple Choice

Is this number divisible by 2?

1,421

• Yes

• No

Multiple Choice

Is this number divisible by 2?

42,377,111,004

• Yes

• No

Multiple Choice

Is this number divisible by 2?

100

• Yes

• No

A number is divisible by 10 if...

• It ends in 0

• 10, 20, 400, 54,330, etc.

Multiple Choice

Is this number divisible by 10?

52

• Yes

• No

Multiple Choice

Is this number divisible by 10?

430

• Yes

• No

Multiple Choice

Is this number divisible by 10?

1,000,000

• Yes

• No

Multiple Choice

Is this number divisible by 10?

7

• Yes

• No

When you divide by 10....

• You take the last 0 away.

• Example: 20 divided by 10 is 2

Multiple Choice

 $50\div10$  

• 50

• 500

• 10

• 5

Multiple Choice

 $400\div10$  

• 4

• 40

• 400

• 10

Multiple Choice

 $\frac{30}{10}$  

• 30

• 20

• 3

• 40

A number is divisible by 5 if...

• The number ends in 5 or 0

• 
  

• 
  

Multiple Choice

Is this number divisible by 5?

551

• Yes

• No

Multiple Choice

Is this number divisible by 5?

5

• Yes

• No

Multiple Choice

Is this number divisible by 5?

110

• Yes

• No

2-digit numbers are divisible by 11 if...

• Both numbers are the same!

• 11, 22, 33, etc.

Multiple Choice

Is this number divisible by 11?

55

• Yes

• No

Multiple Choice

Is this number divisible by 11?

98

• Yes

• No

When you divide a 2-digit number by 11...

• The answer is the repeated number

•  $66\div11=6$  

Multiple Choice

 $44\div11$  

• 44

• 11

• 4

• 10

Multiple Choice

 $99\div11$  

• 9

• 99

• 11

• 88

Other Tips

• If you can divide by 2 twice, it is divisible by 4

• Example: 20 divided by 2 is 10. 10 divided by 2 is 5. Therefore 20 is divisible by 4 ( $20\div4=5$  )

Other Tips

• If the digits add up to a multiple of 3, the original number is divisible by 3.

• Example: 36. 3+6 equals 9, and we divide 9 by 3. Therefore we can divide 36 by 3.  $36\div3=12$   

• Example: 15. 1+5 equals 6, and we divide 6 by 3. Therefore we can divide 15 by 3.  $15\div3=5$   
  

• Remember your 3 times tables! 3,6,9,12,15,...

Multiple Choice

What can we divide 15 by?

• 3

• 4

• Both 3 and 4

• none of these

Multiple Choice

What can we divide 40 by?

• 3

• 4

• both 3 and 4

• none of these

Multiple Choice

What can we divide 12 by?

• 3

• 4

• both 3 and 4

• none of these

Multiple Choice

What can we divide 10 by?

• 3

• 4

• both 3 and 4

• none of these

Simplifying

• The top and bottom number must be divided by the same thing.

What can we simplify  $\frac{14}{24}$  by?

• Both are even.... Divide by 2

•  $\frac{7}{12}$  

What can we simplify  $\frac{5}{10}$  by?

• Both end in a 5 or 0.... Divide by 5

•  $\frac{1}{2}$  

What can we simplify  $\frac{50}{100}$  by?

• Both end in a 0.... Divide by 10

•  $\frac{5}{10}$  

• Both end in 5 or 0.... Divide by 5

•  $\frac{1}{2}$  

Multiple Choice

Simplify:

 $\frac{10}{15}$  

•  $\frac{1}{5}$  

•  $\frac{1}{2}$  

•  $\frac{2}{3}$  

•  $\frac{2}{5}$  

Multiple Choice

Simplify:

 $\frac{2}{8}$  

•  $\frac{1}{8}$  

•  $\frac{1}{2}$  

•  $\frac{1}{5}$  

•  $\frac{1}{4}$  

Multiple Choice

Simplify:

 $\frac{20}{50}$  

•  $\frac{1}{5}$  

•  $\frac{2}{5}$  

•  $\frac{2}{50}$  

•  $\frac{1}{4}$