A gardener has to plant exactly four varieties of flowers in a flower bed, one variety in each of four rows in an ascending order of height from the first row to the fourth row. The seven varieties available to the gardener are, in ascending order of height, red begonias, pink petunias, orange marigolds, red geraniums, white snapdragons, yellow zinnias, and pink cosmos. The following restrictions on color arrangements apply:
No two varieties of the same color can be planted. Orange flowers cannot be planted in a row immediately adjacent to a row of yellow flowers.
Flowers of which of the following colors CANNOT be planted in the third row? Orange Pink Red White Yellow
例二:
Exactly seven people—Q, R, S, T, X, Y, and Z—serve on an advisory board. Q, R, S, and T have been elected to the board, and X, Y, and Z have been appointed to the board. Three-person or four-person panels are sometimes drawn from the board to study proposals. Each panel must include at least one elected and at least one appointed board member, but no panel can consist of equal numbers of elected and appointed members. Each panel is chaired by a person who is a member of the group of board members (elected or appointed) whose representatives are in the minority on that panel. Any panel must also conFORM to the following conditions:
If Q serves on a panel, T cannot serve on that panel. If R serves on a panel, X cannot serve on that panel. T and Y cannot serve on a panel unless they serve together. If Z serves on a panel, X must also serve on that panel.
Each of the following could chair a panel EXCEPT S T X Y Z
第三类问题:
解第3类问题的步骤:(问题中什么都没给,直接就问下面哪一个是coule be,can not be或must be) 1. 迅速看一眼选项,知道选项针对的是什么性质; 2. 看涉及此种性质的条件。问题若是coule be,则找最不固定化的元素;若是can not be或must be,则找最固定化的元素。固定化条件 优先看; 3. 找涉及此元素的选项; 4. 对选项加以验证。(若时间紧,也可以不验证)
若选项未提供有用信息,则立刻从数目和隐式条件着手。
例: Six musicians—Ann, Betsy, Gordon, Juan, Marian, and Ted—are planning to perFORM a program consisting entirely of three quartets. Each quartet requires two violins, one cello, and a piano. Each person must play in at least one quartet, and each person can play, at most, one instrument in a quartet. No person can play the same type of instrument (violin, cello, or piano) in two successive quartets.