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Divisible by four

This little math trick will show you whether a number is divisible by four or not


So, this is how it works.

Let's look at 1234
Does 4 divide evenly into 1234?

Well for 4 to divide into any number we have to make sure that the last number is even. If it is an odd number, there is no way it will go in evenly.
So, for example, 4 will not go evenly into 1233 or 1235

So now we know that for 4 to divide evenly into any number the number has to end with an even number.

Back to the question...

4 into 1234




What you do is this:


Take the last number and add it to 2 times the second last number.


If 4 goes evenly into this number then you know that 4 will go evenly into the whole number.

4 + (2 X 3) = 10
4 goes into 10 two times with a remainder of 2 so it does not go in evenly.

Therefore 4 into 1234 does not go in completely.

Lets try 4 into 3436546
So, from our example, take the last number, 6 and add it to twice the penultimate number, 4

6 + (2 X 4) = 14
4 goes into 14 three times with two remainder.
So it doesn't go in evenly.

Let's try one more.

4 into 212334436

6 + (2 X 3) = 12
4 goes into 12 three times with 0 remainder.

Therefore 4 goes into 234436 evenly.