There is a simple pattern for determining if a binary number is odd. what is it and why does this pattern occur

The answer to this question would be the least number (right most number).

If you add an even number with even number, the result should be even. But if there is just one odd number added, it will be odd.
In binary, all the number is multiplied by . It is pretty clear that all the number should be even beside the first/lowest multiplier  which has potential to be 1. 

Is there a picture to go along with this