染雾ＧＲＥ全真考试题八
There will be seven performers in a talent show: a guitarist, a hypnotist, a juggler, a magician, a pianist, a singer, and a ventriloquist. Exactly three of the performers—the guitarist, the pianist, and the singer—will each require a recorded musical accompaniment. The schedule for the show has seven consecutive time slots. Each of the seven performers will appear in exactly one time slot, and each time slot will have exactly one performer appearing in it. The schedule must follow the rules below:
The juggler must appear first.
The ventriloquist cannot appear immediately after the magician.
At most two performers requiring a recorded musical accompaniment can appear in succession.
Which of the following is an acceptable schedule for the last four performers in the show?
Fourth Fifth Sixth Seventh
Juggler Hypnotist Guitarist Pianist
Guitarist Magician Ventriloquist Singer
Magician Pianist Singer
Singer Guitarist Pianist Hypnotist
Ventriloquist Hypnotist Magician Singer
答案：(E)
这是一道非常简单的排列题，但是分析题在于你会不会做，而在于你花了几分钟把它做完，在于速度。我们通过讲解几道题来体会一下如何迅速定位答案。
读题：7个表演者g,h,j,m,p,s,v参加表演，其中3个g,p,s有音乐伴奏。有7个位置，一人一个。
写条件：
1、j=1 (表示j在第一个位置)
2、～mv (表示v不能出现在m的后面)
3、～(gps) (表示需要音乐伴奏的3人中最多只有2人连续)
条件总结：
**注意g.p.s为等价元素（当然，如果在问题中又出现新的限制条件后，就不一定是）
If the ventriloquist appears third, the singer appears fifth, and the pianist appears sixth, which of the following must be true?
The guitarist appears second.
The guitarist appears fourth.
The hypnotist appears second.
The magician appears fourth.
The magician appears seventh.
答案：(A)
If the singer appears third and the pianist appears fourth, the guitarist must ap
