Question 560066: If I have 6 objects labeled A-F and I need to know how many different combinations that can be made but each combination MUST include object A, how would I figure this out? And the combinations aren't limited to having to have 6 letters...for example, A by itself is a combination. AB, AC,AD, and DA,EA,FA are all combinations. Any help?
Answer by sudhanshu_kmr(1152)   (Show Source):
You can put this solution on YOUR website!
Number of combinations having only one object = 1C1 = 1 i.e A
because every combination must include object A.
number of combinations having two objects = 5C1 = 5
as we have to choose another 1 out of other 5 objects, A has been chosen already.
similarly,
number of combinations having three objects = 5C2 = 10
total number of possible combinations = 1 +5C1 + 5C2 + 5C3 +5C4 +5C5
if any doubt, feel free to ask....
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