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Question
How many different selections of 4 books can be made from 10 different books, if
two particular books are always selected;
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Solution
Two particular books are selected from 10 books. So, 2 books need to be selected from 8 books.
Required number of ways if 2 particular books are always selected =\[{}^8 C_2 = \frac{8}{2} \times \frac{7}{1} = 28\]
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