Question

How many different sets of two-letter initials can you make using the letters D, G, M, S, and T if you can use each letter only once in a set?

Answer 1

DG, DM, DS, DT GD, GM, GS, GT MD, MG, MS, MT, SD, SG, SM, ST, TD, TG, TM, TS. Those are all the possible combinations using each letter only once in each set.

In short, you can make 20 sets.