(help)prep' math

zrj57

sorry, i can not type the chinese

177.      18457-!-item-!-187;#058&011601

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 the 6th year, the tree was 1/5 taller than it was at the end of the 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

in this one,

a1=4 

a6=a4+0.5 

n=6

d should be 0.1 ? 

I don't understand . what's worng with the question?

3x  

snake37

I don't understand your trouble:
equation: 4+6x=6/5(4+4x)
so x=2/3

The answeris D

zrj57

以下是引用snake37在2009/8/20 9:10:00的发言：
I don't understand your trouble:
equation: 4+6x=6/5(4+4x)
so x=2/3

The answeris D

I see

I just got confused the number of 1/5 and think about 2d=1/5.

thank you so much and you have a great day!