Question

Solve by simplifying the problem. There 18 students in Mr. Alvarez's art class . Throughout the year, every student must pair up with every other student to complete a project. How many projects will be finished?

Answer 1

154, since 17+16+15...+1 = 154.
. . . . . . . . . . . . . . . . . .
let each of these dots represent a student. once the first student has finished a project with everyone, cover it with your finger. then, the next student has to do a project with all the others, but not the one behind him, because the one behind him already did a project with him. Am I making sense?