问题 解答题

某商店将每个进价为10元的商品,按每个18元销售时,每天可卖出60个,经调查,若将这种商品的售价(在每个18元的基础上)每提高1元,则日销售量就减少5个;若将这种商品的售价(在每个18元的基础上)每降低1元,则日销售量就增加10个,为获得每日最大利润,此商品售价应定为每个多少元?

答案

设每个售价为x元,每日利润为y元.

若x≥18时,销售量为60-5(x-18),每个利润为(x-10)元,

那么每日利润为y=[60-5(x-18)](x-10)=-5(x-20)2+500,

此时,售价定为每个20元时,利润最大,其最大利润为500元;

若x<18时,销售量为60+10(18-x),每个利润为(x-10)元,

那么每日利润为y=[60+10(18-x)](x-10)=-10(x-17)2+490,

此时,售价定为每个17元时,利润最大,其最大利润为490元;

故每个商品售价定为20元时,每日利润最大.

答:为获得每日最大利润,此商品售价应定为每个20元.

阅读理解

阅读下面短文,从各小题所给的四个选项中选出能够回答所提问题或完成所给句子的最佳答案。

       Is bicycling hard to learn? Different people have many different answers. It is strange enough that the

same person may also have a different answer as time goes by.

       Five years ago when l was in Junior Grade One, I got interested in bicycling because I thought my

uncle was very cool when he rode his bike. He could ride a bike with only one wheel. He could also sit

on the bike and keep it standing straight, without moving for a long time.

       I thought it was easy to learn to ride a bike, so I decided to learn from my uncle.  He told me how to

ride. When I fell off the bike the first time,1 was afraid to try again.  It was too hard for me to learn.

       Then my uncle helped me by holding the bike for me and not to let go. With his help,I was able to

ride longer and longer.  "You can do it by yourself now, young boy!"I heard his voice far behind me.

1. At first, the writer thought it was____ to ride a bike.      

A. easy    

B. different    

C. necessary    

D. important

2. According to this passage,____ is good at bicycling.

A. the writer's father    

B. the writer's brother

C. the writer's uncle    

D. the writer's P. E. teacher

3. The writer learned to ride a bike____.

A. when he was in Junior Grade One    

B. when he was five years old

C. in 2004    

D. when he bought a new bike

4. Which of the following is RIGHT?

A. The writer was always brave when riding a bike.

B. Some people think bicycling is easy.

C. The writer found it easy to ride a bike all the time.

D. The writer's uncle wasn't much good at bicycling.

5. What's the passage about?

A. Bicycling is interesting.    

B. Bicycling is dangerous.

C. Is bicycling easy or hard?    

D. Is bicycling good or bad?

选择题