You can put this solution on YOUR website! Easier formula to remember and use:
5P2 means a permutation of 5 things taken 2 at a time. Start with the first number (which in this case is 5), and count down for a total of 2 numbers:
5P2 = 5*4 = 20
No extra charge for a few more:
5P3 means to start with 5 and count down for a total of 3 numbers:
5P3 = 5*4*3 = 60