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Tree Growth

by ashforgmat » Wed May 12, 2010 6:25 am
When a tree was planted it was 4 feet. Its height increased by a constant amount each year for 6 years. After 6 years the tree was 1�5 taller than at the end of 4th year. By how many feet did the height of the tree increase each year?
a. 3�10
b. 2�5
c. 1�2
d. 2�3
e. 6�5
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by liferocks » Wed May 12, 2010 6:58 am
Let the rate of growth be x
height at the end of 4th yr=4+4x
height at the end of 4th yr=4+6x

so 4+6x-4-4x=1/5(4+4x)
or 10x=4+4x
or 6x=4
or x=2/3

ans option D
"If you don't know where you are going, any road will get you there."
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by gmatmachoman » Wed May 12, 2010 8:02 am
Series : a , (a+d) ,(a+2d) ,(a+3d) ,(a+4d),(a+5d),(a+6d)

Given :

a+6d= (a+4d)+(1/5){(a+4d)}

solving we get d = 2/3
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by HPengineer » Wed May 12, 2010 6:31 pm
2/5 seems like the right answer to me...
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by ashforgmat » Wed May 12, 2010 8:52 pm
Thanks all...
The correct answer is 2/3
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