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（文科）设x，y满足约束条件
x+y≤1
y≤2x
y≥
1
2
x
，则目标函数z=6x+3y的最大值是______．
答案

满足约束条件

x+y≤1
y≤2x
y≥
1
2
x
的可行域如图，

由图象可知：

目标函数z=6x+3y过点A（

2
3
，
1
3
）时

z取得最大值，zmax=5，

故答案为5．

单项选择题

The "Karat" marking on jewelry tells you what proportion of gold is mixed with other metals. If 14 parts of gold are mixed with 10 parts of base metal, the combination is called 14-Karat (14K) gold. The higher the Karat rating, the higher the proportion of gold in the object. The lowest Karat gold that can be marketed in the United States is 10-Karat gold. Jewelry does not have to be marked with its Karat quality, but most of it is. If there is a Karat quality mark, next to it must be the U.S. registered trademark of the person or company that will stand behind the mark, as required by the National Gold and Silver Stamping Act.

If a ring is stamped 24K, it has________.

A．204 parts of gold

B．24 parts of gold

C．two and four-tenths parts of gold

D．10 parts of gold
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单项选择题

______是数据说明、可执行语句等程序对象的集合，它是单独命名的而且可通过名字来访问。

A．模块化

B．抽象

C．精化

D．模块
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