Mathematics for IGCSE & O level - Probability (Section 3 - No. 20)
What is the probability of drawing a red ball, not replacing it, and then drawing a red ball again, if there are 7 red balls and 3 yellow balls to begin with?
49/100
7/15
7/30
7/10
Giải thích
(7/10) * (6/9) = 42/90 = 7/15.