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Lumber Yard Problem

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by RickH » Sun Aug 15, 2010 7:09 pm
Please help me with the following problem:

In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. How many boards are in the stack?
I always get 36 but it should be 34?
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by thirst4edu » Sun Aug 15, 2010 9:03 pm
RickH wrote:Please help me with the following problem:

In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. How many boards are in the stack?
I always get 36 but it should be 34?
Given,
20th board from top = below 16th from bottom
That means 20th from the top is actually 15th from bottom.
Hence, there are 19 boards above 15th from the bottom, which is 19+15 = 34!

Hope this helps!
"Learning never exhausts the mind."
--Leonardo da Vinci
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by RickH » Mon Aug 16, 2010 4:57 am
Thanks, now I see. It's always these kinds of problems that just mess up my Quant score
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by Mayur Sand » Mon Aug 16, 2010 9:40 am
Iam still not clear on this problem . can some one explain in more detail
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by RickH » Mon Aug 16, 2010 10:08 am
Would there be also a way to do it visually?
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by kvcpk » Tue Aug 17, 2010 3:18 am
RickH wrote:Would there be also a way to do it visually?
1,2,3,...........18,(19/16)(20/15),14.......3,2,1

Now count them 18+1+1+14 = 34

Hope this helps!!
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by Makushr1 » Tue Aug 17, 2010 6:50 am
I did it real quick by making dots on a piece of paper representing the lumber. Did 20 going down then went back up. Just make sure u read it carefully since the 20th is BELOW the 16th.
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by anantbhatia » Tue Aug 17, 2010 11:07 pm
From top:
1 2 3 4 ..... 18 19 20
x x x x ..... 17 16 15 ... 3 2 1 From Bottom

Total:18 (from top already counted) + 16 (from bottom already counted)= 34
or
19+15
or so on.. Just a simple counting problem. Hope that helps. Avoid drawing dots or logs :) Use numbers instead.
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