Question

A bag contains 3 black balls 14 green balls and 5 yellow balls.
If two balls are picked at random without replacement , find the probability that balls are of the same colour.
How many black balls must be added so that the probability drawing black balls is a half.

Answer 1

Help now please I am in a hurry.

Answer 2

P(black,black) = 3/22 * 2/21
Similarly for the other colors.
Then just add all three values for P(any,same)

Then, you want (3+x)/(22+x) * (2+x)/(21+x) = 1/2
hmm ... I do not get an integer answer...