Divisibility Rules

Question 1

How do you know if the number is divisible by 2?

Answer 1

Even

Question 2

How do you know if the number is divisible by 3?

Answer 2

You sum all the digits and see if they sum to a number divisible by 3.

Question 3

How do you know if the number is divisible by 4?

Answer 3

Ends in 00
or
Last two digits are divisible by 2

Question 4

How do you know if the number is divisible by 5?

Answer 4

Ends in 0 or 5

Question 5

How do you know if the number is divisible by 6?

Answer 5

Divisible by 3 and 2

Question 6

How do you know if the number is divisible by 8?

Answer 6

Ends in 00
or
Last 3 digits are divisible by 8

Question 7

How do you know if the number is divisible by 9?

Answer 7

Sum up all the digits and see if the sum is divisible by 9.

Question 8

How do you know if the number is divisible by 11?

Answer 8

Alternate + and - all digits and see if sum is divisible by 11.
Ex: 31415, 3-1+4-1+5 = 10 , not divisible
Ex: 2728, 2-7+2-8 = 11, yes divisible