请教两道数学题目，谢谢了！

yinshengsss · 发表于 2010-7-22 11:04:55

Q25:
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

A.   0
B.   1/9
C.   2/9
D.   1/3
E.   1
这个题目答案是C，请教解法谢谢！

Q20:
A collection of 36 cards consists of 4 sets of 9 cards each. The 9 cards in each set are numbered 1 through 9. If one card has been removed from the collection, what is the number on that card?
(1)    The units digit of the sum of the numbers on the remaining 35 cards is 6.
(2)    The sum of the numbers on the remaining 35 cards is 176.
答案是D，
没读懂题目~~请教下~~谢谢！

fly12404 · 发表于 2010-7-22 11:22:45

1.
一個乘客玩三次問都做不同台車的機會是多少
三個選擇玩三次共有3的3次方可能
3個選擇玩三次每次都玩到不同的車的可能性有3!
所以,
3! / 3^3 = 6/27 = 2/9
2.
有一組合組合裡有四組牌一組牌有9張卡分別有號碼1~9
也就是組合裡有36張牌四張1 四張2....四張九
也可以因此算出這整個組合的數字加總是多少
問你抽一張牌出來可以知道那個號碼嗎?
1) 剩下的牌數字加總後的個位數==> CORRECT
2) 剩下的牌的加總數 ===> CORRECT

yinshengsss · 发表于 2010-7-22 20:18:57

明白了，非常感谢fly的热心解答！

请教两道数学题目，谢谢了！

所属分类: GMAT考试

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