问题 选择题

若自然数n使得三个数的加法运算“n+(n+1)+(n+2)”产生进位现象,则称n为“连加进位数”.例如:2不是“连加进位数”,因为2+3+4=9不产生进位现象;4是“连加进位数”,因为4+5+6=15产生进位现象;51是“连加进位数”,因为51+52+63=156产生进位现象.如果从0,1,2,…,99这100个自然数中任取一个数,那么取到“连加进位数”的概率是(  )

A.0.88

B.0.89

C.0.90

D.0.91

答案

当n=0时,0+1=1,0+2=2,n+(n+1)+(n+2)=0+1+2=3,不是连加进位数;

当n=1时,1+1=2,1+2=3,n+(n+1)+(n+2)=1+2+3=6,不是连加进位数;

当n=2时,2+1=3,2+2=4,n+(n+1)+(n+2)=2+3+4=9,不是连加进位数;

当n=3时,3+1=4,3+2=5,n+(n+1)+(n+2)=3+4+5=12,是连加进位数;

当n=4时,4+1=5,4+2=6,n+(n+1)+(n+2)=4+5+6=15,是连加进位数;

故从0,1,2,…,9这10个自然数共有连加进位数10-3=7个,

由于10+11+12=33个位不进位,所以不算.

又因为13+14+15=42,个位进了一,所以也是进位.

按照规律,可知0,1,2,10,11,12,20,21,22,30,31,32不是,其他都是.

所以一共有88个数是连加进位数.概率为0.88.

故选A.

阅读理解

 A man named Smith was sitting on his roof during a flood, and the water was up to his feet. Before long a fellow in a canoe passed and shouted, "Can I give you a lift to higher ground?"

  "No, thanks," said Smith. "I have faith in God and he will save me."

  Soon the water rose to Smith's waist. At this point a motor boat pulled up and someone called out, "Can I give you a lift to higher ground?"

  "No, thanks, I have faith in God and he will save me."

  Later a helicopter flew by, and Smith was now standing on the roof with water up to his neck. "Grab the rope, "shouted the pilot. "I'll pull you up."

  "No, thanks," said Smith. "I have faith in God and he will save me. "But after hours of struggling with water, poor exhausted Smith drowned and went to his reward. As he arrived at the Pearly Gates, Smith met God and complained about this. "Tell me, God, "he said, "I had such faith in you to save me and you let me drown. What happened?"

  To which God replied, "What do you want from me? I sent you two boats and a helicopter."

 小题1:When the pilot asked Smith to grab the rope, ______.

A.Smith pulled the pilot up

B.Smith did so

C.Smith didn't do so

D.Smith didn't hear him小题2:At last, poor exhausted Smith drowned and ______.

A.went to his reward

B.passed away

C.went to heaven

D.all of the above 小题3:What do we know about Smith? ______.

    A. He was a lazy man

    B. He was a lucky man who believed in God

    C. He was a poor man

小题4:What do you think of this passage? This passage is very ______.

    A. moving    B. humorous   C. depressing   D. surprising

     D. He was a silly man who believed in God

多项选择题