Probability Puzzles
Medium
3 min
A bag contains 4 red balls and 6 blue balls. Two balls are drawn without replacement. What is the probability that both are red?
Hint
Calculate the probability of red on the first draw and red on the second draw.
Answer
2/15.
Explanation
The probability of red on the first draw is 4/10. After drawing a red ball, 3 red balls remain among 9 total balls. Therefore the probability is (4/10) × (3/9) = 12/90 = 2/15.
Step-by-Step Solution
P(first red) = 4/10.
P(second red | first red) = 3/9.
P(both red) = 4/10 × 3/9 = 2/15.
P(second red | first red) = 3/9.
P(both red) = 4/10 × 3/9 = 2/15.