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When a certain tree was first planted

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sanjay
 Post subject: When a certain tree was first planted
 Post Posted: Sun Nov 01, 2009 2:25 pm 
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Students


Posts: 10
GMAT prep test-1.
When a certain tree was first planted, it was 4 feet tall, and the height of the tree increased by a constant amount each year for the next 6 years. At the end of 6th year, the tree was 1/5 taller than it was at the end of 4th year. By how many feet did the height of the tree increased each year?

A. 3/10
B. 2/5
C. 1/2
D. 2/3
E. 6/5

OA is D.

Seems so easy, though. I tried hard, but unable to figure out the equation for the problem. Some one please help me figure it out.

Thanks
Sanjay
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alok.sarsidharan
 Post subject: Re: When a certain tree was first planted
 Post Posted: Mon Nov 02, 2009 9:25 am 
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Students


Posts: 7
Let the increase per year = x

Therefore, height of the tree at the end of the 6th year is : 4 + 6x

Also, it is given that : At the end of 6th year, the tree was 1/5 taller than it was at the end of 4th year.

Height of the tree at the end of the 4th year = 4 + 4x

The tree was 1/5 taller than it was at the end of 4th year can be translated as follows :

[4 + 4x] + [1/5 (4+4x)]

Therefore ,
4 + 6x = [4 + 4x] + [1/5 (4+4x)]
Solve for x, answer is 2/3.
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sanjay
 Post subject: Re: When a certain tree was first planted
 Post Posted: Tue Nov 03, 2009 8:06 am 
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Students


Posts: 10
Thanks Alok,

I realized the mistake I was making in doing such a small calculation. Some times you are so caught up with the figure, that your mind does not take any figure, but the wrong figure..
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Ben Ku
 Post subject: Re: When a certain tree was first planted
 Post Posted: Thu Dec 03, 2009 4:09 am 
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ManhattanGMAT Staff


Posts: 824
Good explanation, Alok!

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Ben Ku
Instructor
ManhattanGMAT
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