Mathematical pyramid

Here is a math pyramid. Students start with a given number and divide the number into two. Each number is thus divided into two equal parts. When the number is odd, they must be almost equal numbers, but of course one of them has one more. At the bottom of the pyramid, the numbers are smaller but when we add them all up, the sum corresponds to the number at the top of the pyramid! It's magic!

 Provide a 61 cm X 91 cm (36X24 inch) erasable whiteboard