In how many ways 2 doors be selected from 3 doors for entering and leaving the room?
1) 1
2) 3
3) 6
4) 9
50 12
1) 1
2) 3
3) 6
4) 9
50 12
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Selecting door
Source: Beat The GMAT — Problem Solving |
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talaangoshtari
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3C1 = 3, so in 3 ways we can choose a door. Since the doors for entering and leaving the room are the same, the answer is 3
Last edited by talaangoshtari on Wed Jul 01, 2015 10:38 pm, edited 1 time in total.
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Ian Stewart
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It's not clear what the question means, because the wording is not precise. I'd assume that we can use the same door to enter and leave, and that it matters which door we use to enter, and which we use to leave. Under those assumptions, we have 3 choices for the enter door, and 3 for the exit door, so 3*3 = 9 choices in total.
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I think question is asking to choose 2 doors out of 3 in a room.
1 to enter & 1 to leave
A,B,C are three doors & we need to choose 2 doors where order matters. - so answer is 3!/1! = 6
A,B
B,A
A,C
C,A
A,B
B,A
1 to enter & 1 to leave
A,B,C are three doors & we need to choose 2 doors where order matters. - so answer is 3!/1! = 6
A,B
B,A
A,C
C,A
A,B
B,A
Assuming different doors to be used:
The problem can be divided in 2 steps.
1) First select the door(assuming doors can be differentiated based on something).
3 ways
2) Then choose which door to use for entry and exit.
2 ways
Total ways 3*2 = 6 ways
The problem can be divided in 2 steps.
1) First select the door(assuming doors can be differentiated based on something).
3 ways
2) Then choose which door to use for entry and exit.
2 ways
Total ways 3*2 = 6 ways
It all depends on whether you can use the same door to enter and leave. The GMAT would specify, I think, so this isn't the best question.
