Mathematics for IGCSE & O level - Probability (Section 5 - No. 35)
A box contains 4 red and 6 blue balls. Two balls are drawn at random without replacement. What is the probability that both balls are red?
2/5
2/15
1/15
4/15
Giải thích
The probability of drawing a red ball on the first draw is 4/10. Given a red ball was drawn, the probability of drawing another red ball is 3/9. Therefore, the probability of both is (4/10) * (3/9) = 12/90 = 2/15