a house has exactly eight different doors in how many ways i

Solution

Total different doors = 8

Condition: enter through one door and leave by different door

possible ways to choose a entry door = 8C1 = 8

Possible ways to choose a exit door = 7C1 = 7

(As he cannot choose the entry door again, so remaining doors = 7)

Total number of ways for this condition will be = 8C1* 7C1

= 8*7

= 56 ways