A box contains three white and four red balls. Two balls are drawn randomly in sequence. If the first draw resulted in a red ball, the probability of getting a second red ball in the next draw is
Options:
(A) 0.33
(B) 0.50
(C) 0.67
(D) 0.75
Official Answer Key:
B
Step-by-Step Solution & Explanation
• Total balls initially = 3 white + 4 red = 7. This is sampling without replacement.
• After the first draw removes one red ball, 6 balls remain: 3 white and 3 red.
• P(second ball red | first ball red) = 3/6 = 0.50.
• Distractor logic: (A) 0.33 ≈ 2/6 (wrongly removes two red balls); (C) 0.67 = 4/6 (forgets to remove the first red ball from the red count); (D) 0.75 mixes up totals.
• Final Answer: (B) 0.50
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