Make all possible number using the digits 1 , 3 , 7?
First of all I want to know how many number will be there and then the method to form the number?
Assuming those digits cannot repeat, there are different ways to arrange those digits. Hence there are 6 different numbers that can be made.
Another way of looking at it is that say I have those digits 1, 3, and 7.
Then I could place them in three spots _ _ _.
Choose a digit, lets say the 1. I can place that 1 in any of those three spots, e.g. _ _ 1. So far we have .
Now choose another digit, lets say the 7. There are only two spots where the 7 could be placed, so we have . Lets say we place it like so, 7 _ 1.
Now there is only one spot where the digit 3 can go so we have . Thus there are 6 different possible numbers.