Question 41145: Someone please help me solve these two problems!!!Please!
Section a.
A jar contains 13 black and 12 red marbles. If one marble is drawn at random, what is the probability that it is black?
Section b.
If two marbles are drawn randomly from the jar in section a., what is the probability that the first is red and the second is black if the marbles are drawn....
a.with replacement?
b.Without replacement?
Answer by mszlmb(115)   (Show Source):
You can put this solution on YOUR website! A jar contains 13 black and 12 red marbles.
If one marble is drawn at random, what is the probability that it is black?
If two marbles are drawn randomly from the jar in section a., what is the probability that the first is red and the second is black if the marbles are drawn....
With replacement?
Without replacement?
The first one is easy, it is 13 (for there are 13 blacks) over the total, 13+12=25. The answer to the first is 13/25, or 52%.
The probability of drawing a red one first is 12/25 or .48 . After that, since we are replacing the red one in the jar, the probability of getting a black one is 13/25. The probability of one happening first then the other is 12/25*13/25, which equals 156/625, or 24.96%.
The probability of the same but no replacement has the same probability for 1 black one, 13/25. Then, we still have 12 red ones, but out of 24 total. The answer is thence 13/25*12/24. Why is it 24 instead of 25? Because we don't replace the marble we took. 12/24=.5 so the probability without replacement is .5(13/25), or 13/50, equaling 26%.
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