Chapter 2

Section 2.1

Divisibility Rules

Rule for 2•If the number ends with an even digit

(like 2,4,6,8,0),

then it is divisible by 2. •Example: 1,354,908

Rule for 5• If the number ends with a digit of “5” or “0”,

then the number is divisible by 5.

•Example: 3,627,905

8,394,410

Rule for 10•If the number ends in a “0” digit,

Then the number is divisible by 10.

Example: 750,230

Rule for 3• If you add up the digits of the number and the total is divisible

by 3,

Then the original number is divisible by 3.

Example: 1,248 = 1+2+4+8 =15.

15 is divisible by 3, therefore

so is 1,248!

Rule for 9• If you add up the digits ofthe number and the total is divisible by 9,

Then the original number is divisible by 9.

Example: 6,543 = 6+5+4+3 =18.

18 is divisible by 9, therefore

so is 6,543.

Rule for 4• If the last two digits in the number are divisible by 4,

Then the original number is divisible by 4.

Example: 358,912

12 is divisible by 4, therefore so is 358,912!

Rule for 6• If the number is divisible by 2

and 3,

then it is also divisible by 6.

Example: 8,346.

8,346 = last digit even (divisible by 2)

8,346 = 8+3+4+6 = 21 (divisible by 3)

So also divisible by 6!