SOLUTION: An urn contains 6 green and 7 red marbles. Five marbles are selected. In how many ways can this be done where at least one marble is red?

Question 1151261: An urn contains 6 green and 7 red marbles. Five marbles are selected. In how many ways can this be done where at least one marble is red?
Answer by ikleyn(52781) (Show Source): You can put this solution on YOUR website!
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From the context, the marbles differ by their colors only (since the opposite is not stated).


Let R be the number of red marbles among 5 selected marbles.


Then the number of different cases (the number "in how many ways can this be done") is equal to the number of solution to this inequality


    1 <= R <= 5.


The number of solution is 5.


Therefore, the ANSWER to the problem's question is 5.

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