Question

A cola company decides to test five different brands of soft drink. The different brands have been labeled F, G, H, I, and J. The company decides to compare each brand with the other brands by pairing them together. How many different pairs will result from selecting two different brands at a time?

Answer 1

Cola F can go with G,H,I,J (4 pairs) - Cola G can go with H,I,J (3 pairs) - Cola H can go with I,J (2 pairs) - Cola I can go with J (1 pair)
As a result there are ten total pairs.