Problem Solving

Explanation needed.

2/5 = 12/30

Need 18 yellow balls for P=2/5
So 19 yellow balls would give P<2/5

C

Why not 20 ball, that also give a probabality <2/5

because, the question is asking to find the minimum possible number of yellow balls, which is 19.

Given: The probability that a random ball take from the bag is blue < 2/5

What the probability of taking a blue ball? 12/(12+y) (desired outcome/total possibilities)

So, from the inputs given, 12/(12+y) < 2/5 ==> 12+y > 30 ==> y > 18. Since the question is asking for least number of yellow balls, the answer has to 19.


Good question. Thanks for posting.

Thanks for a good explanation! It's perfect!