Question 1

There are 5 doors to a lecture room. What is the number of ways that a student enters the room and leaves it by different doors?

1. 10
2. 9
3. 20
4. 625
5. 1024

The correct Answer is 20 ways and the correct Choice is (C).

There are 5 doors to the lecture room.
The student would have entered the lecture room using one of the 5 doors in 5 ways.

Now, if she has to leave the lecture room by a different door, then she has to take one of the remaining 4 doors.
She can select one of the four doors to exit the lecture room in 4 ways.

Therefore, the total number of ways a student enters the lecture room and leaves it by different doors = 5 * 4 = 20 ways.

TOPGRE's intensive GRE preparation classes is a 10-weekend 60 hours program. Classes during weekends at our Mylapore Center @ Chennai. Expert Faculty. Small batch size. Next batch on Sep 13, 2008.

Here is what our students have to say about our classroom program for GRE. Our students have made it to some of the top graduate schools in the US.

Get on top of your GRE preparation. Get free practice questions periodically sent by mail. Plus have your queries answered by peers and experts.