问题 解答题

某商场购进一批单价为16元的日用品,销售一段时间后,经调查发现,若按每件20元的价格销售时,每月能卖360件;若按每件25元的价格销售时,每月能卖210件.若每月销售件数y(件)与价格x(元/件)满足关系式y=kx+b.

(1)确定y与x的函数关系式,并指出x的取值范围;

(2)为了使每月获得利润为1800元,问商品应定为每件多少元?

答案

(1)根据题意得:

20k+b=360
25k+b=210

解得:

k=-30
b=960

则y与x之间的函数关系式为:y=-30x+960.

(2)设利润M,则M与x的函数关系式是:

M=(-30x+960)(x-16).

即M=-30x2+1440x-15360

当M=1800时,即-30x2+1440x-15360=1800,

解方程得:x1=22,x2=26,

即为了获得1800元的利润,商品价格每件应定为22元或26元.

阅读理解

Mr. King lived with six hundred wild(野生)animals on the Greek Island of Kyklos. Ever since he left school, he had traveled all over the word collecting animals for his own zoo. He hoped to collect(收集) two examples of every kind of animal on his island(岛屿). But he was afraid that people would find him someday.

He wrote books about his travels and about his animals that he collected. The money from the books helped to pay for all the food that these animals ate.

One day, when Mr. King was out looking for drinking water, he found oil(石油). He needed money for his travels and for his zoo, and a little oil would buy enough water for what he needed all his life, but he knew that if he told anyone else about it, it would be the end of his zoo and his life’s work. So he decided not to tell anyone else about what he had found, because oil and water couldn’t mix.

小题1:.  . Mr. King traveled all over the world for collecting ______.

A.oil

B.water

C.animals

D.money小题2:.  . Mr. King was afraid that people would find him someday because ________.

A.he hadn’t got enough money for them

B.that would be the end of his zoo

C.he hadn’t got enough water and oil

D.they would buy his animals小题3:.  . Mr. King wrote books to _______.

A.tell people about his story

B.tell people how to find oil

C.get enough money for his animals

D.make money for his travels小题4:.  . In the passage, “oil and water couldn’t mix” means that “_________”.

A.Mr. King needed not only water but also oil

B.oil and water were rather difficult to be mixed together

C.Mr. King’s animals only needed water, not oil

D.if he told the others he found oil, his life’s work would be stopped

单项选择题