A bag holds 5 red and 3 blue beads. Two beads are drawn one after the other without replacement. What is the probability that both are red?
Answer and explanation
Correct answer: D. 5/14
- Step 1: P(first red) = 5/8. Step 2. After one red is removed, P(second red) = 4/7. Step 3. Multiply: 5/8 x 4/7 = 5/14. Answer: 5/14. Why not the others: 25/64: That would be true only if the first bead were put back. 25/56: That forgets that one red bead has already been removed, so only 4 red remain. 67/56: Probabilities of successive events are multiplied, not added.
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