Question

Acellus A Suppose you choose four books to read from a summer reading list of 12 books. How many different combinations of books are possible? Note: = n! r!(n-r)!

Answer 1

There are 495 different combinations.

Step-by-step explanation

Picking 4 books to read out of 12 books, with the order of picking unimportant is evaluated as ¹²C₄

`\begin{gathered} ^(1)^(2)C_(4)=(12!)/(4!(12-4)!)=(12!)/(4!*8!)=(12*11*10*9*8!)/(4!*8!) \\ =(12*11*10*9)/(4*3*2*1) \\ =495 \end{gathered}`

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