[求助]蓝皮书数学DS题第90题、第104题

lujibo

90. One kilogram of a certain coffee blend consists of x kilogramof type I coffee and y kilogram of type II coffee. The cost of the blend is C dollars per kilogram, where C=6.5x+8.5y. Is x<0.8?

(1)y>0.15

(2)C>=7.30

我觉得答案是C，但是参考答案是B。死活搞不明白，求助大虾。

104. What was Casey's total score for eighteen holes of golf?

(1)Casey's score for the first nine holes was 13 less than his score for the last nine holes.

(2)Twice Casey's score for the last nine holes was 58 more than his score for the first nine holes.

这个题完全没有搞明白，不知道golf什么规矩阿，没有打过。求助大虾。

[此贴子已经被作者于2009-6-2 23:55:35编辑过]

cdcdcdd

90 c=6.5x+8.5y=6.5x+8.5(1-x)=8.5-2x

104 简单的二元一次方程

lujibo

看来我还是别考了