AN URN CONTAINS 3 RED MARBELS AND 7 WHITE MARBELS. A MARBLE IS DRAWN FROM URN AND A MARBLE OF THAT COLOUR IS THEN PUT IN TO THE URN. A SECOND MARBLE IS DRAWN FROM THE URN. IF BOTH MARBELS WERE OF SAME COLOUR, WHAT IS THE PROBABILITY P THAT THEY WERE BOTH WHITE?

Question

AN URN CONTAINS 3 RED MARBELS AND 7 WHITE MARBELS. A MARBLE IS DRAWN FROM URN AND A MARBLE OF THAT COLOUR IS THEN PUT IN TO THE URN. A SECOND  MARBLE IS DRAWN FROM THE URN. IF BOTH MARBELS WERE OF SAME COLOUR, WHAT IS THE PROBABILITY P THAT THEY WERE BOTH WHITE?

anonymous · Answer

ANS IS 7/8

alekos · Answer

not sure how the arrived at that answer.

P(white) = 7/10 on the first draw, and would also be 7/10 on the second draw
which would give you a total probability of 49/100?

anonymous · Answer

EVEN I THINK THE QUESTION IS WRONG. BT IF U CONSIDER WITHOUT REPLACEMENT, THEN THW ANSWER IS CORRECT.

alekos · Answer

without replacement it should be 7/10 x  6/9  = 7/15

bibby · Answer

Stop yelling dude

anonymous · Answer

USE BAYES THEORAM.
EVENT E=2WHITES + 2REDS =7/15 + 1/15 = 8/15.
THEN P = 2WHITES/E=7/15/8/15=7/8

alekos · Answer

not sure about that because the final result is two white marbles.
i dont believe p(red) should be considered

anonymous · Answer

ITS BAYES THEORAM, U WILL HAVE TO CONSIDER 2REDS

alekos · Answer

i dont think that bayes theorem applies

anonymous · Answer

I WILL TRY TO FIND MORE ABOUT THIS

anonymous · Answer

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