I can't find any posts on this question. Hope this is not a re-post.
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 alphabetic 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
Ans = B
My answer is A. Maybe I didn't get through the question. My understanding is: can use SINGLE letter or 2 letters. So only need 4 alphabets. 4 letters + 4*3 > 12
Please help!作者: chaseconsult 时间: 2012-3-30 20:43
x + C(2,x)>12 ->x at least is 5作者: soubixl 时间: 2012-3-31 06:51