PROBABILITY 2

A bag contains 12 red balls and 8 blue balls. Two balls are taken from the bag. What is the probability that they are both blue?

Solution

(This is a problem with replacement)

n(R) = 12, n(B) = 8, n(S) =20

P(B) = n(B)

            n(S)

1st pick = 8/20

2nd pick = 8/20 as well.

P(B) =  8      x    8

           20          20

P(B) =   64    =      4 

            400          25  

Therefore Probability of drawing a blue ball is 4/25     

TRY THIS ..............

A bag contains 10 purple stones and 12 blue stones. Two stones are taken from the bag. What is the probability that they are both blue?