The probability of picking a blue ball will be 12 divided by the total number of balls. Since the total number of balls will be 12+y, we want y to be a number such that
12/(12+y) < 2/5
Cross multiply to get
60 < 24+2y
36<2y
18<y
Therefore, y must be at least 19 for the probability of selecting a blue ball to be less than 2/5
12/(12+y) < 2/5
Cross multiply to get
60 < 24+2y
36<2y
18<y
Therefore, y must be at least 19 for the probability of selecting a blue ball to be less than 2/5
