A box has 6 red and 3 white marbles. Two marbles are taken out at the same time. What is the probability that both are red?
Answer and explanation
Correct answer: D.
- Step 1: Total ways to choose 2 marbles: .
- Step 2: Ways to choose 2 red marbles: , so .
Answer
.
Why not the others: : it treats the marbles as drawn with replacement. : it counts one red and one white. : the probabilities are added.
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