Originally Posted by

**tmas** I'm having trouble with the last part of this question:

A combination lock has 60 numbers on it, from 0 to 59

A) how many 3 number combinations are possible

60^3 = 216000

b) How many three number combinations are there that do not repeat any numbers in the combination

60nPr3 = 205 320

c) using parts a and b determine how many three number combinations have at least two numbers the same

This is the question that I do not understand how to get, here is what I did:

60nPr2 = 3540 60^2 = 3600

I added these numbers together and got

7140

This is the wrong answer though... the correct answer is 10680