Can 6384 be divided by 6?
Well, it's even, so that's OK. Let's add up the digits: 6 + 3 + 8 + 4 = 21. 3 goes into 21, so 6384 passes both tests. Yes, it can be divided by 6.
What about dividing by 9?
To see if a number can be divided by 9, we add the digits up once - and then we add them up again! If 3 goes into the answer, 9 will go into the original number.
Here's an example:
Can 7102116 be divided by 9? If we add up all the digits, we get 18. Then we add up the digits in our answer: 1 + 8 = 9. Three goes into 9, so 9 will go into 7102116.
Lastly, let's take a massive number (over 2 billion!) and see whether it can be divided by 3, 6 and 9:
The number is 2,715,311,112
Adding up the digits comes to 24. That's in the answers to the 3 times table, so we know that our big number can be divided by 3.
But our big number is also even. So, it's passed both tests which tell us that it can be divided by 6.
What about dividing by 9? Well first we add up all the digits. We've just done that, the answer is 24. Then we add up the digits in our answer: 2 + 4 = 6. That's in the answers to the 3 times table, so yes, our big number can be divided by 9.
Chris