Permutations and Combination

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Permutations and Combination

by BTGmoderatorRO » Fri Dec 29, 2017 9:20 am
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

OA is B
Source: — Problem Solving |