Question

A box contains 6 red balls and 5 green balls. three balls are selected at random from this box "with replacement". what is the probability that exctly two of the three balls are green?

Answer 1

--------------------------------------------
Given information
--------------------------------------------
Red balls = 6
Green balls = 5

--------------------------------------------
Find total
--------------------------------------------
Total balls = 6 + 5
Total balls = 11

--------------------------------------------
Find probability
--------------------------------------------
G = green
R = red
P (R+ G + G) = 6/11 x 5/11 x 5/11 = 150/1331
P (G +R + G) = 5/11 x 6/11 x 5/11 = 150 /1331
P (G +G + R) = 5/11 x 5/11 x 6/11 = 150 /1331
Total probability = 150/1331 + 150 /1331 + 150 /1331 = 450/1331


--------------------------------------------
Ans: The probability is 450/1331
--------------------------------------------