Hi I really need some better explanation for this, not answered well anywhere!
Gmat prep problem - Expert's help preferred
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 370
- Joined: Sat Jun 11, 2011 8:50 pm
- Location: Arlington, MA.
- Thanked: 27 times
- Followed by:2 members
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
Each time the ball descends a level, it has 2 options: to fall TO THE LEFT or TO THE RIGHT.
Since the ball descends 3 levels, and there are 2 options for each level, the total number of routes = 2*2*2 = 8.
There is only 1 way to land in slot 1 (straight down the left side of the triangle) and only 1 way to land in slot 4 (straight down the right side of the triangle).
Each of the 6 remaining routes leads to the one of the two middle slots.
Since the probability of landing in either of the two middle slots is the same, 3 of these 6 remaining routes lead to slot 2.
Thus, P(slot 2) = 3/8.
The correct answer is D.
Since the ball descends 3 levels, and there are 2 options for each level, the total number of routes = 2*2*2 = 8.
There is only 1 way to land in slot 1 (straight down the left side of the triangle) and only 1 way to land in slot 4 (straight down the right side of the triangle).
Each of the 6 remaining routes leads to the one of the two middle slots.
Since the probability of landing in either of the two middle slots is the same, 3 of these 6 remaining routes lead to slot 2.
Thus, P(slot 2) = 3/8.
The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
-
- Master | Next Rank: 500 Posts
- Posts: 370
- Joined: Sat Jun 11, 2011 8:50 pm
- Location: Arlington, MA.
- Thanked: 27 times
- Followed by:2 members
-
- Master | Next Rank: 500 Posts
- Posts: 242
- Joined: Fri Aug 01, 2008 8:49 am
- Location: Delhi
- Thanked: 6 times
[quote="GMATGuruNY"]Each time the ball descends a level, it has 2 options: to fall TO THE LEFT or TO THE RIGHT.
Since the ball descends 3 levels, and there are 2 options for each level, the total number of routes = 2*2*2 = 8.
[color=red]There is only 1 way to land in slot 1 (straight down the left side of the triangle) and only 1 way to land in slot 4 (straight down the right side of the triangle).
Each of the 6 remaining routes leads to the one of the two middle slots.[/color]
Since the probability of landing in either of the two middle slots is the same, 3 of these 6 remaining routes lead to slot 2.
Thus, P(slot 2) = 3/8.
The correct answer is [spoiler]D[/spoiler].[/quote]
Please explain the red coloured portion as I could not understand it.
Since the ball descends 3 levels, and there are 2 options for each level, the total number of routes = 2*2*2 = 8.
[color=red]There is only 1 way to land in slot 1 (straight down the left side of the triangle) and only 1 way to land in slot 4 (straight down the right side of the triangle).
Each of the 6 remaining routes leads to the one of the two middle slots.[/color]
Since the probability of landing in either of the two middle slots is the same, 3 of these 6 remaining routes lead to slot 2.
Thus, P(slot 2) = 3/8.
The correct answer is [spoiler]D[/spoiler].[/quote]
Please explain the red coloured portion as I could not understand it.
-
- Senior | Next Rank: 100 Posts
- Posts: 57
- Joined: Mon Dec 21, 2009 6:27 am
- Location: Melbourne, Australia
- Thanked: 17 times
- sam2304
- Legendary Member
- Posts: 1239
- Joined: Tue Apr 26, 2011 6:25 am
- Thanked: 233 times
- Followed by:26 members
- GMAT Score:680
To hit cell numbered 1, the ball has to come all the way left, if it goes right anywhere in the middle it won't hit cell 1. So there is only 1 way. [see the picture if you don't understand it] Similar manner to hit 4 it has to go all the way right - one way. Total 8 ways, one for cell 1, one for cell 4 and remaining 6 for cell 2 and 3.There is only 1 way to land in slot 1 (straight down the left side of the triangle) and only 1 way to land in slot 4 (straight down the right side of the triangle).
Each of the 6 remaining routes leads to the one of the two middle slots.
Please explain the red coloured portion as I could not understand it.
Getting defeated is just a temporary notion, giving it up is what makes it permanent.
https://gmatandbeyond.blogspot.in/
https://gmatandbeyond.blogspot.in/