Understand the Divisibility Rules for 2, 3, 5 and 10

Instead of actually carrying out a division, it is possible to test a number to see if it can be divided exactly by certain numbers.

 

If a number divides exactly into a number, it is divisible by this number.

 

24 is divisible by 2 because 24 ÷ 2 is a whole number.

24 is not divisible by 5 because 24 ÷ 5 is not a whole number.

 

Here are the rules to test divisibility by 2, 3, 5 and 10.

 

Rule for 2

A number is divisible by 2 if it ends in 0, 2, 4, 6 or 8.

This means that it is even.

 

Rule for 3

A number is divisible by 3 if the sum of its digits is divisible by 3

3045 is divisible by 3 because 3 + 0 + 4 + 5 = 12 which is divisible by 3

3044 is therefore not divisible by 3 because 11 is not divisible by 3.

 

Rule for 5

A number is divisible by 5 if it ends in 0 or 5.

3045 is divisible by 5 because it ends in 5.

3030 is divisible by 5 because it ends in 0.

5551 is not divisible by 5.

 

Rule for 10

A number is divisible by 10 if it ends in 0.

3140 is divisible by 10 because it ends in 0.

3145 is not divisible by 10.

 

Example

Is 3813 divisible by 3?

 

Answer

Yes, because 3 + 8 + 1 + 3 = 15, which is divisible by 3.

 

Are you happy with all this?

 

 

Then let's get started!