问题 解答题

小明父母的服装店开业了,销售一种服装,进价40元/件,现每件以60元出售,一星期卖出300件.小明对父母的服装店很感兴趣,因此,他对市场作了调查.调查结果如下:如降价,每降价1元,每星期可多卖出20件;如涨价,每涨l元,每星期少卖出10件.请问同学们,如何定价才能使一星期利润最大?

答案

设一星期所获利润为y,若每件涨价x元,根据题意得,

y=(60+x-40)(300-10x)

=-10x2+100x+6000

=-10(x-5)2+6250(0≤x≤30),

∵a=-10<0,

∴x=5,y有最大值6250,

即定价为65元时,所获利润最大,最大利润为6250元;

若每件降价x元,根据题意得,

y=(60-40-x)(300+x)

=-20x2+100x+6000

=-20(x-2.5)2+6125(0≤x≤20),

∵a=-20<0,

∴x=2.5时,y有最大值6125,

即定价为57.5元时,所获利润最大,最大利润为6125元.

综上所述,定价为65元时,才能使一星期利润最大,最大利润为6250元.

阅读理解

阅读理解。

      A great French writer has said that we should help everyone as much as possible because we often

need help ourselves. The small even can help the great. To this effect , he tells the following simple story.

      An ant was drinking at a small stream and fell in. She made desperate efforts to reach the side, but

made no progress at all. The poor ant, almost exhausted, was still bravely doing her best when a dove

saw her. Moved with pity the bird threw her a blade(叶片) of grass, which supported her like a raft,

and thus she reached the bank again. While she was resting and drying herself in the grass she heard a

man approaching. He was walking along barefooted and carrying a gun in his hand. As soon as he saw

the dove he wished to kill her, and he would certainly have done so, but the ant bit him in the foot just

as he raised his gun to fire. He stopped to see what had bit him, and the dove immediately flew away.

It was an animal much weaker and smaller than herself that had saved her life.

1. According to the French writer, we often need help from others, therefore we should _______.

A. help others as much as we can  

B. help those who may be useful to us

C. get as much help as possible    

D. help others in order to keep alive

2. An ant fell in the stream and could not reach the bank ________. 

A. because she did not try hard      

B. because she tried too hard

C. because she did not cry for help  

D. no matter how hard she tried

3. The ant finally got on the side _______.

A. when the water pushed her

B. with the help of a blade of grass given by a dove

C. with the help of a piece of wood

D. when the dove reached out a leg for her

4. According to the passage, which of the following does the author express?

A. the dove was quite brave        

B. the ant's cleverness

C. how an ant saved a bird        

D. that even the small can help the great

单项选择题