Step by step
The question
Question: is 4326 divisible by 3 and 9?
Divisible means it goes in exactly, with nothing left over.
1 Add the digits
We add the digits: 4 + 3 + 2 + 6 is 15.
Why add the digits?
Each ten is 9 and 1 more.
Each hundred is 99 and 1 more.
3 and 9 go into the 9s and 99s.
What is left over is the sum of the digits.
For 3: 15 divided by 3 is 5, nothing left over.
So 3 goes into 4326.
For 9: 15 divided by 9 is 1, with 6 left over.
So 9 does not go into 4326.
Careful!
For 9, the sum must divide by 9, not only by 3.
15 divides by 3, but not by 9.
2 Write the answer
So 4326 is divisible by 3.
Not by 9.
3 Check
Let's check by dividing.
4326 divided by 3 is 1442, nothing left over.
4326 divided by 9 is 480, with 6 left over.
The tests were right!
Let's look back.
First: add the digits.
Then: write the answer.
Last: check.