PROBABILITY C9

A bag contains 3 red pencils and 2 blue pencils and 3 green pencils. Three pencils are taken from the bag. What is the probability that they are all blue?

Solution

(This is a problem with replacement)

n(R) = 3, n(B) = 2, n(G) = 3, n(S) = 8

P(B) = n(B)

            n(S)

1st pick = 2/8

2nd pick = 2/8 as well,

2nd pick = 2/8 as well.

P(B) =   2      x   2    x     2

             8           8           8

P(B) =    8    =       1 

             512         64  

Therefore Probability of drawing a blue pencil is 1/64    

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

 
A bag contains 5 red pencils and 7 blue pencils and 8 green pencils. Three pencils are taken from the bag. What is the probability that they are all green?