已选分类
理学数学
单选题Last year, a certain public transportation system sold an average (arithmetic mean) of 41,000 tickets per day on weekdays (Monday through Friday) and an average of 18,000 tickets per day on Saturday and Sunday. Which of the following is closest to the total number of tickets sold last year? (A) 1 million (B) 1.25 million (C) 10 million (D) 12.5 million (E) 125 million
单选题如下图所示，小正方形的被阴影所覆盖，大正方形的被阴影所覆盖，则小、大正方形阴影部分面积之比为______A．B．C．D．E．
单选题一辆客车、一辆货车和一辆小轿车在同一条直线上朝着同一方向行驶，在某一时刻，货车在中，客车在前，小轿车在后，且它们的间距相等．走了10分钟，小轿车追上了货车；又走了5分钟，小轿车追上了客车．则再过______分钟，货车追上了客车．
单选题若有意义，则x的取值范围为()．
单选题设有二维随机变量(X，Y)，已知D(X)=9，D(Y)=4，X，Y的相关系数为，则D(X-Y)=______。A.15B.9C.13D.5
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单选题设D：|x|+|y|≤1，则A．0B．C．D．1
单选题|x|＜|x
3
|
(1)x＜-1 (2)|x
2
|＜|x
4
|
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单选题圆与圆C2：x2-6x+y2一8y=0有交点．
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单选题连续型随机变量X的分布函数其中的常数a和b为A．B．C．D．
单选题已知三个不等式：(1)x
2
-4x+3＜0，(2)x
2
-6x+8＜0，(3)2x
2
-9x+m＜0，要是同时满足(1)和(2)的所有x满足(3)，则实数m的取值范围是______。
单选题若向量组α，β，γ线性无关，α，β，δ线性相关，则______
A.α必可由β，γ，δ线性表示
B.p必不可由α，γ，δ线性表示
C.δ必可由α，β，γ线性表示
D.δ必不可由α，β，γ线性表示
单选题函数y1=f(a+x)(a≠0)与y2=f(a-x)的图像关于( )．
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单选题Jerome wrote each of the integers 1 through 20, inclusive, on a separate index card. He placed the cards in a box, then drew cards one at a time randomly from the box, without returning the cards he had already drawn to the box. In order to ensure that the sum of all the cards he drew was even, how many cards did Jerome have to draw?