1. The problem statement, all variables and given/known data Josh works on the second floor of a building. There are 10 doors to the building and 8 staircases from 1st to the 2nd floor. Josh decided that each day he would enter by one door and leave by a different one and go up one stair case and down another. How many days could Josh do this before he had to repeat a path he had previously taken? 2. Relevant equations 3. The attempt at a solution For one day: Possibilities for choosing a door are 10 * 9 For one day: Possibilities for choosing a Stair case are 8 * 7 I dont know after how many days he would repeat the path. Zulfi.