SOLUTION: A box contains 5 white and 4 blue marbles. Two marbles are drawn from the box in succession without replacement. What is the probability of getting a white on the second draw given

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Question 1195505: A box contains 5 white and 4 blue marbles. Two marbles are drawn from the box in succession without replacement. What is the probability of getting a white on the second draw given that it is white on the first draw?
Found 2 solutions by ikleyn, math_tutor2020:
Answer by ikleyn(52790) About Me  (Show Source):
You can put this solution on YOUR website!
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In this problem, we are given that the first draw is a white marble.

It means that after first draw and before the second draw there are 4 white and 4 blue marbles in the box.

Therefore, the probability to draw a white marble at the second draw is 4%2F%284%2B4%29 = 4%2F8 = 1%2F2 = 0.5 = 50%.       ANSWER

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Solved and carefully/thoroughly explained.



Answer by math_tutor2020(3817) About Me  (Show Source):
You can put this solution on YOUR website!

"given that it is white on the first draw" is important phrasing. We know 100% that the first marble is white.

Since the marble isn't replaced, we drop to 5-1 = 4 white marbles remaining out of 5+4-1 = 8 total marbles left.

The probability of getting another white marble is 4/8 = 1/2

Answer: 1/2