A bag holds red and blue counters. Two counters are drawn at random without replacement. What is the probability that both are red?
Answer and explanation
Correct answer: C.
- Step 1: First counter red: .
- Step 2: Second red, given the first was red: (4 red left of 7).
- Step 3: Joint probability .
Answer
.
Why not the others: : treats the draws as with replacement. : is the chance that the second counter is red given that the first was, not the joint chance. : multiplies by for no reason.
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