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sana.noor
- Legendary Member
- Posts: 512
- Joined: Mon Jun 18, 2012 11:31 pm
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i am trying to solve this question in two different ways, one way is easy and i get right answer but the other way is lengthy but i am not getting the right answer, am i doing it right? here is the question and explanation
there are 100 balls in a jar. 40 are black and 60 are white. what is the probability of getting at least one black in three consecutive picks with replace of each ball.
a) .216
b).316
c).5
d).684
e).784
OA is 0.784
one way: 1-(getting no black ball) = 1- (3/5)^3= 0.784 answer
2nd way: 1) getting one black and 2 white= 18/125
2)getting two black and one white = 12/125
3) getting 3 black = 8/125
adding all three cases = 38/125 =.304 and thats the wrong answer, what i am doing wrong here
there are 100 balls in a jar. 40 are black and 60 are white. what is the probability of getting at least one black in three consecutive picks with replace of each ball.
a) .216
b).316
c).5
d).684
e).784
OA is 0.784
one way: 1-(getting no black ball) = 1- (3/5)^3= 0.784 answer
2nd way: 1) getting one black and 2 white= 18/125
2)getting two black and one white = 12/125
3) getting 3 black = 8/125
adding all three cases = 38/125 =.304 and thats the wrong answer, what i am doing wrong here
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