Denis that is an excellent question. Although HT1992 tells us "i am not a mathematician" to a mathematician
between means between.
X is between 41 & 50 means
X∈{42,43,44,45,46,47,48,49}.
On the other hand, if we want
X∈{41,42,43,44,45,46,47,48,49,50} we say "
X is from 41 to 50".
Now to answer HT1992 question
1−(550)(540)≈0.689 SEE HERE
Now I chose to use subsets:
(550) is the number of ways to chose five ,
any five, from fifty.