How many different 3-digit numbers can be formed from the number 1,2 and 3 if the digits do not repeat in the numbers?
three choices for the first digit
2 choices for the second
1 choice for the third
3*2*1 = 6
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1