Question
Tue June 19, 2012 By: Sonali

A bag contains 4 red balls,6green ballsand some white balls.If the probability of not drawing a white ball in one draw be2/3 then find the number of white balls.

Expert Reply
Tue June 19, 2012
Let the number of white balls be n.
Total number of balls = 4+6+n = 10+n
 
P(drawing red ball) = 4/10+n
P(drawing green ball) = 6/10+n
P(drawing white ball) = n/10+n
 
P(not drawing white ball) = 2/3 (Given)
P(drawing white ball) = 1-2/3 = 1/3
 
Therefore, we have:
n/10+n = 1/3
Solve this equation to get the value of n, that is, the number of white balls.
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