A room has 5 doors. In how many ways can a man enter the room through one and come out through a different door?

Asked by Topperlearning User | 4th Jun, 2014, 01:23: PM

Expert Answer:

The man has to perform two jobs in succession:

 

1)     He has to enter the room, then

2)     He has to come out from the room

 

Clearly, a person can enter the room through anyone of the 5 doors, So he can perform first job in 5 ways.  After entering into the room, the man can come out through a different door in 4 ways.

 

Hence the number of ways in which a man can enter a room through one door and come out through a different door = 5 x 4 = 20

Answered by  | 4th Jun, 2014, 03:23: PM