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 作者: momoz 时间: 2011-1-18 16:15
设tree每年长高x feet 第六年末，tree的高度是(4+6x),第四年末，tree的高度是(4+4x) [(4+6x)-(4+4x)]/(4+4x)=1/5 解得x=2/3作者: alexischao 时间: 2011-1-18 16:20
D，2/3作者: haizeiwang8888 时间: 2011-1-18 16:56
By how many feet did the height of the tree increase each year 这句话是什么意思？不是每年增长多少吗作者: haizeiwang8888 时间: 2011-1-18 16:59
谢谢，但是我还是没明白题意~为什么要和第四年比呢？作者: dhr945 时间: 2011-1-18 18:57