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Re: PS : Probability (conditional) [#permalink]
09 Oct 2003, 06:46

praetorian123 wrote:

# 1. A bag has 15 marbles , 7 black, 8 red . You pick 5 marbles one by one. The first four marbles are red.

1. Whats the probability that the fifth marble is red. 2. Whats the probability that the fifth marble is black.

# 2. A box contains 10 balls ,7 green, 3 yellow . You pick 5 one by one. Out of the first three, 2 green and 1 yellow.

Whats the probability that the remaining balls are a GREEN and a yellow ?

Please explain.

Thanks Praetorian

Praet,

#1 - Since it's given that the first 4 are red,
Prob. that 5th is red = 4/11 (We have to find out the probability only for the 5th one to be red and not for all 5 to be red.)
Similarly, Prob. that 5th is black = 7/11.

#2 - I am confused as to what the question means.

Amar.

gmatclubot

Re: PS : Probability (conditional)
[#permalink]
09 Oct 2003, 06:46