SOLUTION: The reading list for a literature class has 7 fiction and 9 nonfiction books. A student is to write a report on 5 books from the list during the semester. The reports must include

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Question 1116838: The reading list for a literature class has 7 fiction and 9 nonfiction books. A student is to write a report on 5 books from the list during the semester. The reports must include at least 1 and at most 4 reports of fiction books. In how many ways can the selection of books be made?
Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
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All possible opportunities are listed in the table below (two most-left columns)


 #of fiction books   #of non-fiction books  #of combinations  value
----------------------------------------------------------------------------

        1                     4              C%5B7%5D%5E1%2AC%5B9%5D%5E4            882
 
        2                     3              C%5B7%5D%5E2%2AC%5B9%5D%5E3           1764

        3                     2              C%5B7%5D%5E3%2AC%5B9%5D%5E2           1260

        4                     1              C%5B7%5D%5E4%2AC%5B9%5D%5E1            315



The third column contains the formulas for the number of selections.

The fourth column contains the values calculated with these formulas:


C%5B7%5D%5E1%2AC%5B9%5D%5E4 = 7%2A%28%289%2A8%2A7%2A6%29%2F%281%2A2%2A3%2A4%29%29 = 882;

C%5B7%5D%5E2%2AC%5B9%5D%5E3 = %28%287%2A6%29%2F%281%2A2%29%29%2A%28%289%2A8%2A7%29%2F%281%2A2%2A3%29%29 = 1764;

C%5B7%5D%5E3%2AC%5B9%5D%5E2 = %28%287%2A6%2A5%29%2F%281%2A2%2A3%29%29%2A%28%289%2A8%29%2F%281%2A2%29%29 = 1260;

C%5B7%5D%5E4%2AC%5B9%5D%5E1 = %28%287%2A6%2A5%29%2F%281%2A2%2A3%29%29%2A9 = 315.


Now your last step is to add all four numbers in the right column:  882 + 1764 + 1260 + 315 = 4221.


Answer.  The selection of books can be made in 4221 ways.