1、In an insurance company, each policy has a paper record or an electric record, or both of them. 60 percent of the policies having incorrect paper record have incorrect electric record and 75 percent of the policies having incorrect electric record have incorrect paper record. 3 percent of all the policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy, what is the probability that it is one having both correct paper and correct electric record?
【答案】94%
【思路】
设总数为X policies,则既有非P又有非E为3%X;60%的非P中为非E,则非P为3%X/60%;75%的非E为非P,则非E为3%/75%,那么非P与非E一共有 ,那么P与E一共有X-,则其概率为/X=94%
2、If for all x, x^2+ax+b = ^2, then a =?
b=0;
c=-3;
【答案】B
【思路】x^2+ax+b = ^2= x^2+2cx+c^2,则A=2C,只要知道C的值就可以知道A值了
x^2+ax+b = ^2= x^2+2cx+c^2
x^2+ax+b = x^2+2cx+c^2
化简后:x+=0
因为对于所有的x值,上式均成立,则a-2c与b-c^2必须同时为0;
a-2c=0
b-c^2=0
只要知道了b或c中的任何一个数,a均可求。
偶选D。
3、随机抽样10个产品有N个坏的,N5,问N=?
任取两个产品,都是坏的可能性为1/15;
任取两个产品,一好一坏的可能性为7/15; 分页标题#e#
【答案】D
【思路】C/C=1/15可算出N=6=32则N=3
CC/C=7/15可算出N=21=37=73则N=3或7,又N5,所以N=3
4、xyz0, 问x0?
|x+y|=|x|+|y|
|y+z|=|y|+|z|
【答案】C
【思路】由可知X、Y是同号,由可知Y、Z也是同号,则X、Y、Z都是同号,所以x0
5、1/a+1/b+1/c+1/d+1/e=1,ae全是不同的正整数,问:a+b+c+d+e的least possible value?
【答案】3+4+5+6+20
【思路】没有特殊的方法,最好能够记住。
下一篇: 费费数学宝典(连载八)
体坛英语资讯:Hosts China suffer third straight defeat at World Womens Curling Championships
2017届高考英语一轮复习知识点专练:冠词
2017届高考英语一轮复习知识点专练:名词
2017届高考英语一轮复习知识点专练:代词
国内英语资讯: More irregularities found in environment inspections in China
2017届高考英语一轮复习知识点专练:定语从句
2017届高考英语一轮复习语法专练:9 情态动词和虚拟语气(牛津译林版含解析)
2017届高考英语一轮复习知识点专练:听力模拟题组二
国际英语资讯:At least 16 killed in waterfall accident in Ghana
2017届高考英语一轮复习知识点专练:特殊句式
2017届高考英语一轮全册复习学案:Unit19《Language》(北师大版)
体坛英语资讯:Neymar: Brazil has recovered winning DNA
2017届高考英语一轮复习知识点专练:连词及状语从句
2017届高考英语一轮复习语法专练:4 定语从句(牛津译林版含解析)
2017届高考英语一轮复习知识点专练:名词性从句
“皮皮虾我们走!”用英语怎么说?
电子书销量持续下滑 年轻一代爱上纸质书
体坛英语资讯:Bayern, Schalke win in German Bundesliga
体坛英语资讯:Monaco keep high-flying profile in Ligue 1 title contest
2017届高考英语一轮复习语法专练:11 构词法(牛津译林版含解析)
2017届高考英语一轮复习语法专练:6 名词、冠词和代词(牛津译林版含解析)
2017届高考英语一轮复习知识点专练:非谓语动词
2017届高考英语一轮全册复习学案:Unit18《Beauty》(北师大版)
国内英语资讯: 2 dead, 8 missing after boats sink in east China
2017届高考英语一轮复习知识点专练:听力模拟题组三
2017届高考英语一轮复习知识点专练:动词的时态与语态
娱乐英语资讯:Legendary musician Chuck Berry dies at 90
2017届高考英语一轮复习语法专练:7 形容词和副词(牛津译林版含解析)
2017届高考英语一轮全册复习学案:Unit23《Conflict》(北师大版)
2017届高考英语一轮复习语法专练:5 名词性从句(牛津译林版含解析)