Permutations and Combinations

Question

A student downloaded 5 MUSIC FILES to a portable MP3 player. In how many different orders can the songs be played? 

Answer 1

I'm assuming the 5 files are 5 DIFFERENT songs (otherwise the following solution won't work). Under this assumption there are 5! ways to play the songs. The way to think about this is to ask how many choices are there for the first song (5), how many choices for the second song (4 remaining songs), ..., 1 choice for the last song. Now multiply the number of choices: 5 × 4 × ... × 1 = 120.

Answer 2

I just answered two problems for you. I suggest that you consider answering this one all by yourself.  Just identify the type of problem & use the appropriate principle(s).

 

Is there a key word in the problem that reveals whether it's a combination or permutation situation?