2021 JMPSC Sprint Problems/Problem 10
Problem
Serena gets a grade of 
for her chapter test. She doesn't remember how many problems there were, but she remembers that there were at most 
problems, each problem solved correctly was worth an equal amount of points, and she did not receive any points for an incorrect or skipped question. Find the sum of all the possible numbers of problems that the test could have had.
Solution
Because 
, 
where 
is an integer. This implies that 
is a multiple of 
. The multiples of less than are , 
, 
, and 
, so the answer is 
.
~Mathdreams
