1. Whether a number is divisible by four or not?

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

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

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, the solution:

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.

So

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.

Let’s try 4 into 3436546

So, from our example, take the last number, 6 and add it to

two times 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.

you can use it in working out whether the year you are calculating is a leap year or not.