2023 AMC 12B Problems/Problem 18
Solution
Denote by the average of person with initial
in semester
Thus,
,
,
.
Denote by the average of person with initial
in the full year.
Thus,
can be any number in
and
can be any number in
.
Therefore, the impossible solution is
~Steven Chen (Professor Chen Education Palace, www.professorchenedu.com)