# Mathnasium #MathTricks: Divisibility (Rule for 9s)

May 1, 2022 | Yukon

In this week's math trick, we have another divisibilty trick that skips the long division!  This time, we will be tackling 9's.

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There's an easy and fun way to tell if a number is divisible by 9!  Simply add all the digits of the number and then divide by 9.  If the digits add to a multiple of 9, then the number is divisible by 9! In our example, we use 738.

7 + 3 + 8 = 18

and 18 is a multiple of 9

therefore, 738 is divisible by 9!

For larger numbers, you can also repeat this step you are left with a single digit number.  If you end up with 9, then the number is divisible by 9.

For instance, 322,867

3 + 2 + 2 + 8 + 6 + 7 = 28

28 is not divisble by 9 – but let's say we are not sure of that.

2 + 8 = 10

1 + 0 = 1

≠ 9

Therefore, 322,867 is not divisible by 9.

Think you got the hang of it?  Test out your new math trick with the sample questions below!