between 20 and 28 students signed up for the chess club. The students could not be divided exactly into groups of 2, 3, 4, and 5. how many students signed up for the chess club?

Sagot :

possibilities
20,21,22,23,24,25,26,27,28
2 remove all even
21,23,25,27
3 rules out 21 and 27
 23,25
5 pulls out 25
23 is the answer