请教PREP

endlessfrenz

1. June 25, 1982, fell on a Friday, on which day of the week did June 25, 1987 fall?  ( 1984 was a leap year )

A  Sunday      B  Monday     C  Tuesday    D  Wednesday     E  Thursday

答案选E

这道题目我完全没有思路,不知道它到底考的是什么知识点?

2.  A  certain list of 100 data has an average of 6 and a standard deviation of d, where d is positive, which of the following pairs of data, when added to the list, must result in a list of 102 data with standard deviation less than d?

A -6 and 0    B 0 and 0    C 0 and 6     D 0 and 12    E 6 and 6

答案选E, 同样请教思路, 谢谢!

endlessfrenz

HELP!HELP!!

alicewann

一年有365天
        去除以8 =45…..5
            

June 25, 1982, fell on a Friday 所以
            June 25, 1983 fell on Wednesday. (Friday+ 5days)

以此類推
        但要注意1984 was a leap year (多了2/29) 所以那年要用366天除以8…餘6

注意!! 1987 was also a leap year!

freya1573

第一题我的想法是这样的：

June 25, 1982到June 25, 1987总共5年。所以共5*365=1825天. 但是因为1984是leap year。所以1825+1=1826天。

所以，1826/7=260余6. 余下的6天你来数一数。发现是星期四啦。

第二题其实很简单。只要你真的弄懂什么是标准差。

一堆数字。只要它们越集中在平均数周围。那么这堆数字的标准差就越小。反之就越大。

 E 6 and 6---这个就是平均数了。所以缩小了标准差。(看它的公式）

http://forum.chasedream.com/dispbbs.asp?boardid=22&replyid=3073607&id=126759&page=1&skin=0&Star=1看看这个帖你会有些收获的！

好运啊!

[此贴子已经被作者于2008-9-5 2:56:39编辑过]

endlessfrenz

谢谢freya1573,你的思路很清晰,而且很容易就能懂~~也谢谢你发过来的网页~很有用的

同时也谢谢alicewann啦~