data/problems/371.yml
---
:id: 371
:name: Licence plates
:url: https://projecteuler.net/problem=371
:content: "Oregon licence plates consist of three letters followed by a three digit
number (each digit can be from [0..9]). \nWhile driving to work Seth plays the
following game: \nWhenever the numbers of two licence plates seen on his trip add
to 1000 that's a win.\n\nE.g. MIC-012 and HAN-988 is a win and RYU-500 and SET-500
too. (as long as he sees them in the same trip).\n\nFind the expected number of
plates he needs to see for a win. \nGive your answer rounded to 8 decimal places
behind the decimal point.\n\n**Note:** We assume that each licence plate seen is
equally likely to have any three digit number on it.\n\n"