Question

Of 18 possible​ books, you plan to take 7 with you on vacation. How many different collections of 7 books can you​ take? You can take nothing different collections of 7 books on vacation with you.

Answer 1

31,827 ways

Explanation:

Total number of books, n = 18

Number of books to be selected, r = 7

Since, the order of arrangement doesn't matter ;

We use the combination formula :

nCr = n! ÷ (n-r)! r!

18C7 = 18! ÷ 11!7!

18C7 = (18*17*16*15*14*13*12) ÷ (7*6*5*4*3*2*1)

18C7 = 160392960 / 5040

18C7 = 31,827 ways