How many different groups of 3 letters can be made from the letters A,A,B,B,C,C and D? I know its a combinations question, but the identical letters are putting me off... Someone help me please!

Question

usman1995 · Answer

it's a combination and similar letters are not so serious prob , if u take it as A1 and A2 then u can arrange them as A1A2 or A2A1 so answer will be  7C3

usman1995 · Answer

my medal please

anonymous · Answer

yes, but theyre not A1 and A2, theyre A and A, so they are identical letters, and therefore 7C3 will not give the correct answer.

usman1995 · Answer

hey i was just said that to make u clear in combination repittion can occur right so AA can be written AA or AA i mean it's annoying but it's what it;s like

usman1995 · Answer

combination will involve both A's no matter what so there will be 7C3

anonymous · Answer

AAB: how do you know that is A1A2B1, A2A1B1, A1A2B2, A2A1B2? You cant, because those 4 different combinations are actually the same thing....

usman1995 · Answer

bcz at one A will b there in all combinations (groups) and other A will then again can be used in making other groups in each and every group A will be used and second A will again be used

usman1995 · Answer

yes i can't but i know that i used both those A's in the combinations

usman1995 · Answer

yes if it's a combination then 7C3 is right and if it's a permutation 7!/2!2!2! but it's a combination so it's exactly 7C3