# Combinations (math 30 pure)

1. Dec 12, 2009

### Gokuraku

1. The problem statement, all variables and given/known data
a license plate has 3mos then 3letters then 3nos(numbers) if there are no constraints
how many license plates are possible

2. Relevant equations
9x9x9x9x9x9x9(..maybe)

3. The attempt at a solution
The same as the one above, I am very confused.

2. Dec 12, 2009

### grief

So, if I understand it correctly, the license plate is of the form 123ABC123. There are no constraints, that means the numbers don't need to be unique.

Think about it is a number of slots. In each slots you can put one of several possible values.

What if the license plate was just one number followed by one letter? Try to answer this simpler problem first, and then generalize.

3. Dec 12, 2009

### HallsofIvy

I think by "9x9x9x..." you are referring to the "counting principle". Yes, that can be used here. However, if there are no constraints, so that any of the digits can be 0 to 9, there are 10 digits, not 9. And, of course, there are 26 letters.