SOLUTION: [The question I am having trouble with is 5] 4. A jar contains 13 black and 12 red marbles. If one marble is drawn at random, what is the probability that it is black? [My answe

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Question 156690This question is from textbook Algebra 1 An Incremental Development
: [The question I am having trouble with is 5]
4. A jar contains 13 black and 12 red marbles. If one marble is drawn at random, what is the probability that it is black? [My answer is 13/25]
5. If two marbles are drawn randomly from the jar in prblem 4, what is the probability that the first is red and the second black is the marbles are drawn...
a) with replacement? b) without replacement? This question is from textbook Algebra 1 An Incremental Development

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
4) Correct.



5)
a) With Replacement 


                   # of red marbles      12
P(First is red) = ------------------ =  ----
                  total # of marbles     25


Since you are replacing the marble (ie putting it back), this means that the total number of marbles stays the same 



                      # of black marbles      13
P(Second is black) = ------------------ =  -------
                     total # of marbles       25



-----------------------------------------------------------------------------

b) Without Replacement 

                   # of red marbles      12
P(First is red) = ------------------ =  ----
                  total # of marbles     25



Now since you are NOT replacing the marble, this means that the total number of marbles will go from 25 to 24 


                      # of black marbles            13         13
P(Second is black) = ----------------------    = --------- =  -----
                     total # of marbles - 1         25-1       24

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