作者catspace (柏拉图的永恒...)
看板GMAT
标题Re: [问题] GWD22-Q19
时间Tue Nov 11 21:15:24 2008
※ 引述《yyiitt1003 (怀念补习班的日子)》之铭言：
: 以下问题,实在想不出来思考盲点,请各位高手帮忙解惑了~
: Running at their respective constant rates, macgine X takes 2 days
: longer to produce w widgets than machine Y.At these rates,if the
: machines together produce 5/4w widgets in 3 days,how many days would
: it take machine X alone to produce 2w widgets?
: Ans.12
: A certain roller coaster has 3 cars,and a passenger is equally likely
: to ride in any 1 of the 3 cars each time that passenger rides the roller
: coaster. IF a certain passenger is to ride the roller coaster 3 times,
: what is the probability that the passenger will ride in each of the 3 cars?
: Ans. 2/9
: There are 8 books on a shelf,of which 2 are paperbacks
: and 6 are hardbacks.How many possible selections of 4 books from this
: shelf include at least one paperback?
: Ans. 50
: 做越多题,越来越没信心了..
补充最後一题
用(全部的方法)-(全选精装版)
= (C8取4) - (C6取4) = 55 你应该是看错答案......
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 118.160.169.180
1F：→ yyiitt1003:我的GWD答案给的是50,不过至少我知道解法了,谢谢 11/13 01:36