# Math Help - probability of repeated numberplate

1. ## probability of repeated numberplate

Firstly, I'm not sure this is the right forum, but it's harder than anything I did in high school so I'm putting it here, mods feel free to move it

I don't think it's a hard question, I'm just very rusty with my probability

For a Traffic engineering subject I've conducted traffic counts for a section of road, recording the digits from the number plate (Victorian (AUS) Plates, format ABC 123).

If I've got 'n' results, what's the probability of having a repeated numberplate.

2. this is essentially a bump, but i'll add some more information in keeping with the rules

More specifically, If i record number plates at one location and someone else records number plates at a location down the road, what's the chance that a repeated value is from a different car.

3. For the first letter you have a $\dfrac{1}{26}$ chance of it being the same letter assuming no letters are "banned".

For the second letter, because it's independent of the first you have an equal chance.

Can you take it from here?