其它
Hansel wants to buy 2 dice of different colours. If the available colours in a store are red, blue, green, yellow, pink and white, how many different combinations of 2 dice are there in the store? (Example: 1 combination is yellow and white) 
Overseas Competition->Knowledge Point->Counting Modules->Permutations and Combinations->Combinations
RB, RG, RY, RP, RW  BG, BY, BP, BW  GY, GP, GW,  YP, YW,  PW 