问题 解答题
某售报亭每天以每份0.4元的价格从报社购进若干份报纸,然后以每份1元的价格出售,如果当天卖不完,剩下的报纸以每份0.1元的价格卖给废品收购站.
(Ⅰ)若售报亭一天购进280份报纸,求当天的利润y(单位:元)关于当天需求量x(单位:份,x∈N)的函数解析式.
(Ⅱ)售报亭记录了100天报纸的日需求量(单位:份),整理得下表:
日需求量x240250260270280290300
 频数10201616151310
(1)假设售报亭在这100天内每天购进280份报纸,求这100天的日利润(单位:元)的平均数;
(2)若售报亭一天购进280份报纸,以100天记录的各需求量的频率作为各销售量发生的概率,求当天的利润不超过150元的概率.
答案

(Ⅰ)当x≥280时,y=280×(1-0.4)=168;

当x<280时,y=(1-0.4)x-(280-x)×0.4=0.9x-84

∴y=

0.9x-84,x<280
168,x≥280
,x∈N            …(5分)

(Ⅱ)(1)这100天中,每天利润为132元的有10天,每天利润为141元的有20天,每天利润为150元的有16天,每天利润为159元的有16天,每天利润为168元的有38天,所以这100天的日利润的平均数为

132×10+141×20+15×16+159×16+168×38
100
=154.68.…(9分)

(2)利润不超过150元当且仅当报纸日需求量不大于260份,故当天的利润不超过150元的概率的概率为

P=0.1+0.2+0.16=0.46.…(12分)

阅读理解

For generations here in the deepest South, there had been a great taboo(禁忌): publicly crossing the color line for love. Less than 45 years ago, marriage between blacks and whites was illegal, and it has been forbidden for much of the time since.

So when a great job about an hour’s drive north of the Gulf Coast attracted him, Jeffrey Norwood, a black college basketball coach, had reservations. He was in a serious relationship with a woman who was white and Asian.

“You’re thinking about a life in South Mississippi?” his father said in a skeptical voice, recalling days when a black man could face mortal(致命的) danger just being seen with a woman of another race, regardless of intentions. "Are you sure?"

But on visits to Hattiesburg, the younger Mr. Norwood said he liked what he saw: growing diversity. So he moved, married, and, with his wife, had a baby girl, who was counted on the last census(人口普查) as black, white and Asian. Taylor Rae Norwood, three, is one of thousands of mixed-race children who have made this state home to one of the nation's most rapidly expanding multiracial populations, up 70 percent between 2000 and 2010, according to new data from the Census Bureau.

In the first comprehensive accounting of multiracial Americans since statistics were first collected about them in 2000, reporting from the 2010 census, made public in recent days, shows that the nation’s mixed-race population is growing far more quickly than many researchers had estimated, particularly in the South and parts of the Midwest. That conclusion is based on the bureau’s analysis of 42 states; the data from the remaining eight states will be released soon.

In North Carolina, the mixed-race population doubled. In Georgia, it grew by more than 80 percent, and by nearly as much in Kentucky and Tennessee. In Indiana, Iowa and South Dakota, the multiracial population increased by about 70percent.

Census officials estimated the national multiracial growth rate was about 35 percent since2000 according to the known result, when seven million people ----- 2.4 percent of the population ------ chose more than one race.

小题1:If a black man married a white woman 50 years ago, the worst result was that _____.

A.he was sentenced to death

B.he was considered to be immoral

C.he was criticized by the public

D.he was treated as a lawbreaker小题2:The underlined word “serious” in Paragraph 2 can be replaced by “____”.

A.stable

B.bad

C.mixed

D.dangerous小题3:What can we infer from Paragraph 4?

A.Jeffrey Norwood was born in Hattiesburg and grew up there.

B.Taylor Rae Norwood’s mother is a white-Asian.

C.70 percent of the people in Mississippi are multiracial.

D.Mississippi has the largest multiracial population in the US.小题4:Which of the following states had the fastest growth rate of mixed-race population?

A.Georgia.

B.Tennessee.

C.North Carolina.

D.South Dakota.

单项选择题