Best Answer

The easiest way is to test it. Divide the number by 9, and see if the result is an even number, or if there is a fractional amount in the answer. This is quite easy to do with a calculator, but can be done by hand as well, if you know how to do long division.

To test a number without doing the division:

Add the digits of the number together and if this sum is divisible by 9 then so is the original number.

The sum can be tested in the same way, so repeatedly add the digits of the sum until until a single digit remain. If this digit is 9 then the original number is divisible by 9; otherwise it gives the remainder when the original number is divided by 9.

This single digit result is called the digital root of the number.

A quick way of getting this single digit is that whilst summing the digits of the number if the sum ever exceeds 9 subtract 9 from the sum (which can be done by adding the two digits together); this means if the digit 9 appears in the number it can be ignored (unless the number is entirely made up of 9s, in which case the number is [clearly] divisible by 9).

For example is 413796453981 divisible by 9?

413796453981

4 + 1 = 5

5 + 3 = 8

8 + 7 = 15 → 1 + 5 = 6 (or 15 - 9 = 6)

next digit 9 can be ignored as: 6 + 9 = 15 → 1 + 5 = 6 (or 15 - 9 = 6)

6 + 6 = 12 → 1 + 2 = 3 (or 12 - 9 = 3)

3 + 4 = 7

7 + 5 = 12 → 1 + 2 = 3 (or 12 - 9 = 3)

3 + 3 = 6

next digit 9 can be ignored as: 6 + 9 = 15 → 1 + 5 = 6 (or 15 - 9 = 6)

6 + 8 = 14 → 1 + 4 = 5 (or 14 - 9 = 5)

5 + 1 = 6

→ 413796453981 is not divisible by 9 and has a remainder of 6 when the division is done.

Study guides

☆☆

Q: How do you know a number is divisible by 9 if?

Write your answer...

Submit

Still have questions?

Related questions

If the digits of a number add up to a multiple of 9, the whole number is divisible by 9.

If its digital sum add up to 9 then it is divisible by 9

yes, you know that because if you add the digits together and that number is divisible by 9, then that large number is divisible by 9. 3+4+2 is 9, which is divisible by 9. conclusion 342 is divisible by 9.

It is divisible by 9.

Every number is divisible by 9 but the answer wont necessarily be a whole number.

It's very easy to test a number to see if it is divisible by 4 or by 9. If it passes both tests, then it is divisible by 4x9=36.To test for divisibility by 9, add the digits of the number. If the sum is divisible by 9, then the number is divisible by 9.To test for divisibility by 4, look at the last two digits. If they are a multiple of 4, then the number is divisible by 4.

The easiest way to know if a number is divisible by 9 is to add the digits in the number. 4 + 7 + 8 + 8 = 27 Since 9 will go into 27 evenly, 4788 is divisible by 9.

If a number is not divisible by 3 then it is not divisible by 9.

it is really simple, all you have to do is add all the numbers in the number and see if it is divible by nine!Hope that helped!

Yes, every number that's divisible by 9 is divisible by 3

Yes, any number divisible by 9 is also divisible by 3.

add all the digits of the number and check if it is divisible by 3. eg-3321=3+3+2+1=9=divisible by three.the same works for 9.

People also asked