Question

there are 12 marbles in a bag, and the marbles are either yellow or green. Two marbles will be randomly picked from the bag, without replacing the first one picked. How many YELLOWS marbles are in the bag given that the probability that both marbles will be yellow is 5/33

Answer 1

Let us assume that the number yellow balls are x, so the number of green balls are 12-x.

The probability that both marbles will be yellow is

(x/12) X (x-1)/11 = 5/33

(x(x-1))/132 = 5/33

(x(x-1))/4 = 5

(x(x-1)) = 5X4

(x(x-1)) = 20

we then get 12-5 , x=5

So we can conclude that thew number of yellow marbles is 5 and the number of green marbles is 7.