How many different selections of 4 books can be made

varitero5w

varitero5w

Answered question

2022-06-22

How many different selections of 4 books can be made from a bookcase displaying 12 books?

Answer & Explanation

Sydnee Villegas

Sydnee Villegas

Beginner2022-06-23Added 22 answers

Step 1
X 12 C 4 = 12 ! ( 12 - 4 ) ! 4 ! = 12 × 11 × 10 5 × 9 4 × 3 × 2 × 1 = 495
For each of the 12 choices that could be made for the first book there would be 11 choices that could be made for the second book then 10 choices for the third and 9 choices for the fourth.
Step 2
So there would be 12 × 11 × 10 × 9 ways of selecting the books but the same 4 books could have been selected in 4 × 3 × 2 × 1 different ways (using the same logic as above).
So the actual number of different selections would be: XXX 12 × 11 × 10 × 9 4 × 3 × 2 × 1

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