A bag holds 4 red balls and 3 blue balls. Two balls are drawn one after the other without replacement. What is the probability that both are red?
Answer and explanation
Correct answer: C. 2/7
- Step 1: First draw red: 4/7. Step 2. With one red removed, the second draw is red with probability 3/6, so the product is 12/42 = 2/7. Answer: 2/7. Why not the others: 16/49 and 12/49 wrongly keep 7 balls for the second draw (replacement), and 4/7 ignores the second draw.
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