# Marble probability Question

A bag contains three red marbles, two green ones, one lavender one, two yellow, and two orange marbles.

How many sets of four marbles include all the red ones?

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I've added the tag combinatorics, which is more suitable. Probably you want to use the result in finding some probability, but the question itself is a combinatorial one. –  Beni Bogosel Apr 17 '12 at 20:45

You have four elements out of which three are red. So you can complete the last position with any of the balls of other colors.

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Without repetition you have 4 colours apart from red so: $4$ ways to add a marble to a set of 3 red ones and therefore $4$ different sets with 3 red marbles.

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