What is (4x10^6) devided by ( 2x10^4) as an ordinary number

Please help

How to do this , and can some one explain

Ateacher noticed 5/8 of the students were wearing either blue shorts or white shorts. write two different ways this could be done.

Astuntman jumping off a 20-m-high building is modeled by the equation h=20-5t^2, where t is the same in seconds. a high-speed camera is ready to film him between 15m and 10m above the ground. for which interval of time should the camera film him?