Divisibility Rules

Making friends with fractions

The rule for “2”

2 goes into every even number…..

Even numbers are numbers that end in 0, 2, 4, 6, or 8

The rule for “3”

3 will go into a number if 3 goes into the sum of the digits

Example: 1,266

The sum of the digits is 1 + 2 + 6 + 6 = 15

3 goes into 15….so 3 goes into 1,266

The rule for “4”

If 4 goes into the last two digits it goes into the number

Example: 240…..4 goes into 40 so 4 goes into 240

The rule for “5”

5 goes into any number that ends in “0” or “5”

The rule for “6”

If 2 and 3 go into a number, so does 6

Example: 132….2 goes into it because it is even….3 goes into it because the sum of the digits is 6….6 goes into it because 2 and 3 do

The rule for “7”

Take the last digit and double it….subtract that from the remaining digits…continue until you get a number that is divisible by 7

Example: 133…take the last digit and double it…..3 x 2 = 6

13 – 6 = 7….7 goes into 7 so 7 goes into 133.

The rule for “8”

Not on our list, because it’s a rotten rule!

If 8 goes into the last 3 digits, it goes into the number.

The rule for “9”

Same as the rule for 3…..if 9 goes into the sum of the digits it goes into the number.

Example: 1,233….the sum of the digits is 9…9 goes into 9 so 9 goes into 1,233

The rule for “10”

10 goes into any number that ends in 0

What will divide evenly into:

• 222

• 224

• 1,200

• 7,011

• 156

• 440

• 812