manelgirona wrote:A doctor must label 12 patients. Each label contains either a single letter or a pair of different letters in alphabetical order. What is the minimum number of letters needed?
a) 4
b) 5
c) 6
d) 10
e) 12
Answer is B
My guess is that trial and error is the quickest way to solve this problem.
Let's start with (a), since we want the minimum number of letters:
4 - let's choose ABCD.
So, our labels are:
A
B
C
D
AB
AC
AD
BC
BD
CD
that's only 10, so not enough.
Now, we're only 2 shy of what we need and adding another letter will add far more than just 2 more possible labels, so pick (B), no need to test.
