PROBABILITY F1

 

A bag contains 4 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) = 4, n(B) = 8, n(S) = 12

 

P(R) = n(R)

            n(S)

 

P(R) = 4

          12

 

1st pick = ⁴/12

2nd pick = ⁴/12 as well.

 

 

P(RR) =  4      x    4

             12            12

 

P(RR) =   ¹⁶ /144 = ¹/9       

 

Therefore Probability of drawing a red ball is 1/9     

 

 

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

 

A bag contains 7 purple stones and 11 yellow stones. Two stones are taken from the bag. What is the probability that they are both purple?