A box contains 5 red balls, 3 blue balls, and 2 green balls. Two balls are drawn at random without replacement. What is the probability that the first ball is red and the second ball is blue?
1/6
1/5
3/20
1/12
Show the answer and explanation
Correct answer
A. 1/6
Principle or equation
For sequential draws without replacement, multiply the probabilities: P(A then B) = P(A) * P(B|A).
Why this answer is correct
Total balls = 10. P(first red) = 5/10 = 1/2. After removing a red, 9 balls remain, 3 blue. P(second blue | first red) = 3/9 = 1/3. Product = 1/2 * 1/3 = 1/6.
Example
If 4 red and 6 blue, P(red then blue) = 4/10 * 6/9 = 4/15.
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