Probability › Drawing from bags › Colour ratios
Guaranteeing a red ball in draws
Middle school · ●○○○○ 10 pts
A bag contains 10 red balls, 8 white balls and 7 black balls. The balls are drawn one by one at random, without replacement. Find the minimum value of such that a red ball is guaranteed to have been drawn by the -th draw (on the -th draw or earlier).