A bag contains 5 red and 7 blue balls. Two balls are drawn without replacement. Find the probability that both are red.
Answer and explanation
Correct answer: C.
- Step 1: First red: . Second red (one fewer ball of each kind): .
- Step 2: .
Answer
.
Why not the others: is what you get if you treat the draws as with replacement. is what you get if you add the probabilities. is what you get if you forget that the total decreases after the first draw.
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