Question

Of 13 possible books, you plan to take 8 with you on vacation. How many different collections of 8 books can you take?

Answer 1

13C8

Answer 2

so u just times 8 by 13

Answer 3

or is it 8!

Answer 4

do u know about combination ? and factorial ?

Answer 5

no

Answer 6

hmmmm... for basic, u must know about factorial, first.
ex. 3! (3 factorial) it means that 3! = 3 * 2 * 1 = 6 and 8! = 8.7.6.5.4.3.2.1 = ... (use calculator :))
now, the formula of combination is nCr = n!/(n-r)!r!,
so 13C8 = 13!/(13-8)!8! = 13!/5!8! = ... calculate it

Answer 7

51,891,840

Answer 8

is that right?

Answer 9

13!/5!8! =13.12.11.10.9.8!/(5.4.3.2.1.8!)
= 13(11)(9) = 1287

Answer 10

are we using the formula for Permutations?

Answer 11

it's combination not permutation

Answer 12

oh yeah....didn't see that.

Answer 13

how did u get 11 and 9