Prep PS1 177

girlwithwings

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

D

请问1/5 taller than it was at the end of the 4th year 如何理解？

本题如何列式？

girlwithwings

谢谢，我一直把constant amount 当作constant rate 所以想着是几次方了。。。

everine

请问1/5 taller than  it was at the end of the 4th year 如何理解？

就是比第四年末高了五分之一啊

设每年高x，那么第六年就是4+6x，第四年是4+4x
高了五分之一，就是4+6x=1.2(4+4x)