Here's the question you clicked on:
anthony~
Find the number of ways to listen to 4 different CDs from a selection of 10 CDs.
There are 15 x 14 x 13 x 12 ways to listen to 4 different CDs out of 15.
i am wrong, @seiga is right
theres are the answer choices: 151,200 5040 2880 720
--151,200 5040 2880 720 --solution: in this case the original answer should be ¹⁰C₄ = (10x9x8x7) / (1x2x3x4) = 210 but from options it is clear that it is used ¹⁰P₄ = 10x9x8x7 = 5040 in the question paper i m still sure that since it is not mentioned track wise or not. so it must be ¹⁰C₄ or 210 as answer. hope it would be helpful