Question

The number of ways to listen to 4 different cds from selection of 15 cds

Answer 1

In general number of choosing r things from the group of n number of things(When order doesn't matter) = $^nC_r$

We can expand $^nC_r$ as $^nC_r = \frac{n!}{r! * (n-r)!}$

So same way we can find number of way to listen 4 different cds from 15 cds  = $^{15}C_4$

Which we can calculate as
$^{15}C_4 = \frac{15!}{4!* (!5 - 4)!} = \frac{15!}{4! * 11!}$
                         $= \frac{15 * 14 * 13 * 12 * (11!)}{4*3*2*1 * (11!)} = \frac{15*14*13*12}{4*3*2*1} = 5* 7 * 13 * 3 *1$
                                                  = 1365

Answer 2

Answer:

 32,760 is the correct answer, the first person is wrong! Took the test and this is it!

Step-by-step explanation: