[問題]有一題DS題

[gwrien]

8.Susan has selected exactly three crayons, each a different color, from a crayon box. How many crayon colors were represented in the box before her selection?

(1)Exactly four distinct three-crayon color combinations were represented in the box before Susan selected three crayons.

(2)Just before Susan's selections, the box contained exactly five crayons.

答案：C
本題出自：《30天GMAT全攻略》, p58, 第8題。

請教各位高手解題過程為何？謝謝~~

[celivia]

看不太懂STATEMENT(1)在說啥
(1)Exactly four distinct three-crayon color combinations were represented in the box before Susan selected three crayons.

我的想法是問:BOX中取3隻蠟筆都不同顏色的條件下會有4種組合
設共有N種顏色, C(N,3)=4 => N=4
Box裡有4種顏色
唯一解---充分選(A)
不過這又與答案不符

[gwrien]

謝謝celivia幫忙解答，我也是選A
原題問盒中原有幾色？題目中可知SUSAN選了三色，所以盒中原本至少有三色
statement(2)不充分，
statement(1)可知組合為：ABC, BCD, ABD, ACD
由(1)可知正好四色
真是太奇怪了，我才想說問問大家

我後來仔細看了一次題目，
(1)Exactly four distinct three-crayon color combinations
應該是指：四種不同的三支蠟筆組合
而不是：四種不同的三色蠟筆組合(...很討厭玩這種文字遊戲)
因此(1)除了ABC, BCD, ABD, ACD(原有ABCD四色)
亦可能出現ABC, AAA, AAB,AAC(原有AAABC三色)的組合
所以(1)也不充分，因為無法確定是三色或四色
(1)+(2)盒中原有五支，可組成四種不同的組合
可知為AAABC，因此可確定有三色
答案為C

希望正式考不要遇到這種題目