请教GWD19-22

yvonnege

Q22:

A researcher plans to identify each participant in a certain medical experiment with a code consisting of either a single letter or a pair of distinct letters written in alphabetical order.  What is the least number of letters that can be used if there are 12 participants, and each participant is to receive a different code?

A.       4

B.       5

C.       6

D.       7

E.        8

Youknowme

B

yvonnege

请教思路，谢谢！

Youknowme

设共选出x个字母

x+C(x,2)>=12

当X为4时，只能区分十个人；当X为5时，可区分15个人

A，B，C，D ，E，AB，AC，AD，AE，BC，BD，BE，CD，CE，DE

the least number of letters 为5

[此贴子已经被作者于2006-3-20 16:43:32编辑过]

yvonnege

谢谢！总算明白什么叫alphabetical order了!