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Old 04-09-2013, 01:46 AM
purshe purshe is offline
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Join Date: Apr 2013
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Default Re: *ANSWER* Homework1 - Q3

One can solve this problem intuitively without applying formulas

Note that we are calculating the probability after the first ball is drawn.
We know there are 4 possible scenarios are possible at the time of drawing the first ball
1: (Bag1, Black1),
2: (Bag1, Black2),
3: (Bag2, Black)
4: (Bag2, White)

Since we have already drawn the first ball & know it is black, we deduce that the 4th option has not occurred. So, we narrow down the possible scenario list to 3

Given this, we need to determine if the second ball will also be black. Out of the three shortlisted options, two of those options will give us the required scenario (option 1 & 2).

Hence probability = 2/3
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