[問題] GWD9-27

[meimei]

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
答案是B....看了之前討論..還是不懂....為什麼壓??...

[JS]

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
答案是B....看了之前討論..還是不懂....為什麼壓??...

The easiest way is to try the answers on.
We need at least 12 sets of numbers so let's pick answer C to start with
C(6,2) = 15 plus the 6 single digits we have 21 sets of numer

now let's try Answer B
C(5,2) = 10 Plus 5 = 15 it's good but try A just to make sure

try Answer A
C(4,2) = 6 plus 4 =10 not enough
So the answer has to be B

[nicoleliu]

建議也可參考OG PS#281題
幾乎是一模一樣的題目喔!