You can surprise anyone by showing how quickly you can calculate whether one number is divisible by 3 or not.

Say 1235678. How you know if it is divisible by 3?

Add all the individual digits of the given number.

That is: (1+2+3+5+6+7+8)=32.

32 is not Divisible by 3. Hence, the given number is not divisible by 3.

If a number is divisible by 3, the sum of all of its individual digits will also be divisible by 3.

Now let's take this number: 17746404.

Add them up:

(1+7+7+4+6+4+0+4)=33.

33/3=11.

So 17746404 is divisible by 3.

Now it's time for you to surprise someone.

Update:

My friend Anshul pointed out the trick is also applicable for 9. Thanks to him.

## 1 comment:

Same goes for 9.

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