Dave wrote this: I was reading the combinations/permutations area of your web page and have a query. You mention that if a bank was allocating 4 digit pins then the number of possible pin numbers would be 5040. I don't understand why. If they can have 0000,0001.....9999, then why are there not 10,000 possible numbers? i.e. 9999 + 1 for 0000 any help would be great cheers dave Good question Dave that shows that I didn't explain that bit of that page fully, so I added a couple of examples to help out. Take a look at my Permutations and Combinations page to see the improvements I made. Thanks for helping out, Dave. DW