PROBABILITY 1

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 red?

Solution

(This is a problem with replacement)

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

P(R) = n(R)

            n(S)

1st pick = 12/20

2nd pick = 12/20 as well.

P(RR) =  12      x    12

               20            20

P(RR) =   9        

                25          

Therefore Probability of drawing a red ball is 16/81     

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

A bag contains 8 purple stones and 14 blue stones. Two stones are taken from the bag. What is the probability that they are both blue?