NandishSS wrote:
gmatt1476 wrote:
The map above shows the trails through a wilderness area. If travel is in the direction of the arrows, how many routes along the marked trails are possible from point A to point B ?
A. 11
B. 18
C. 54
D. 108
E. 432
PS24831.01
Attachment:
2019-09-21_1417.png
HI Experts
GMATGuruNY,
MentorTutoring,
generis,
I'm bit confused here. Why is it not \(2*(3^2)*(3^2)*(3^2)\) ?
Hi NandishSS,
When dealing with certain types of Permutation or Combination questions, it can sometimes help to "put yourself in the story" so that you can logically work through the steps involved in the calculation.
We're told that the map above shows the trails through a wilderness area and travel MUST be done in the direction of the arrows. We're asked for the total number of routes along the marked trails that are possible from point A to point B.
At the first 'step' on the trail, we have 2 options (go "up" or go "down"). After you make that choice....
we then have 3 options ("up" path, "middle" path or "down" path). After you make that choice...
we then have another 3 options ("up" path, "middle" path or "down" path). After you make that choice...
we then have one more set of 3 options ("up" path, "middle" path or "down" path). After you make that choice, you are at the end of the path (Point B).
Thus, the total number of possible routes is:
(2)(3)(3)(3) = 54 different routes
GMAT assassins aren't born, they're made,
Rich
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