求大牛帮忙

zjsnml · 发表于 2013-10-1 22:48:24

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

A. 4

B. 5

C. 6

D. 7

E. 8

这题毫无思路呢，希望会的NN帮忙解答！！

南蛮也爱球 · 发表于 2014-1-13 18:48:07

答案是4

wyw1018 · 发表于 2014-1-13 21:29:06

答案是5
单个字母有5种，双字母有4+3+2+1=10种，所以够分配12个人每人一个没有重复。

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