SOLUTION: From 7 Algebra books and 6 Geometry books, in how many ways can one select 2 Algebra and 2 Geometry books to buy if all the said books are equally necessary?
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Question 1178630: From 7 Algebra books and 6 Geometry books, in how many ways can one select 2 Algebra and 2 Geometry books to buy if all the said books are equally necessary? Answer by ikleyn(52776) (Show Source):
There are = = 7*3 = 21 ways to select 2 Algebra books from 7 Algebra books.
There are = = 3*5 = 15 ways to select 2 Geometry books from 6 Geometry books.
THEREFORE, there are = 21*15 = 315 ways to make that selection, which is prescribed in the problem.
Solved, answered, explained and completed.
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This problem is to use two conceptions of Combinatorics.
One conception is Combinations.
The other conception is the Fundamental counting principle.
