How many four-digit numbers are there between 0 to 9?

all possible 4 digit combinations 0-9

What are all the possible 4-digit codes using the numbers 0-9?0000, 0001, 0002, u2026.

9997, 9998, 9999.

,Basically its all whole numbers between 0 and 9999

4 digit code cracker

Top Ten possible methods to break into a safe:,Hire a locksmith,Hire a safe-cracker,Crowbar,Sledgehammer,Circular saw with diamond blade,Impact drill with diamond bit,Cutting torch,Thermal lance or burning bar,Pipe bomb,Nitro-glycerin

All 10,000 4 digit combinations

u201cHow do you open a combination lock with 4 numbers?u201dBrute force.

,By that, I donu2019t mean that you force the lock open.

I mean that you create a system for going through all 10,000 combinations, and then you go through them, one at a time.

,I once found an abandoned padlock on my front porch.

It looked like this:,I would have been happy to return it to its owner, but no one claimed it.

So now I have a padlock, which would have been useful, if I could only open it!,So I made a chart of the letters, and started testing them in order.

Set a combination, pull on the hasp, sigh, advance the bottom dial one click, repeat.

Do that ten times, then advance the next dial one click and keep going.

Check from time to time to make sure Iu2019m where I ought to be, to make sure I didnu2019t miss anything.

,I was able to check 100 combinations in about two minutes.

It was boring, so I carried the padlock with me and fiddled with it in odd moments; if I had two minutes to kill, Iu2019d test the next 100 combinations.

From time to time Iu2019d jot down where I was in the list.

,I think I was about two-thirds of the way through the 10,000 possible combinations when the padlock opened.

(Huzzah!) It took me about a week.

,I wound up giving it to my youngest stepdaughter.

I showed her how to change the combination to something memorable; she was delighted.

She used it for a while, with great success, until she moved out and left it behind.

(Fortunately, I knew what combination she had usedu2026 so I didnu2019t need to go through the whole thing again!!),UPDATE:nWow, almost 3,000 upvotes! Many thanks!,Many people are telling me, in the comments, that there are tricks to cracking a padlock like this in only a few tries.

I appreciate the advice and the tricks, and Iu2019ve tried to learn from themu2026 but so far, I have not succeeded in using any of them to open one of these padlocks.

,Moreover, I see this as a metaphor.

Sometimes the quickest way to solve a problem is to figure out what all the possibilities are, and just go through them in order.

,(Mathematicians did that, some years back, with the computer-generated proof of the four-color map theorem.

Many suspected that any two-dimensional map could be colored with just four colorsu2026 but try as they might, they couldnu2019t prove it.

So two mathematicians used brute force, listing every possible pattern group, and proving that every one could be done with just four colors.

They donu2019t like that method, but it got results, and now the question is answered.

),If you know how to beat a padlock like this, then you can do so, and my hatu2019s off to you.

But if you donu2019t, then doing it my way will work for just about anybodyu2026 and itu2019s good practice in thinking about problems this way.

100 most common 4 digit PINs

YES,It falls into multiple categories.

,If you hand the card to a person at a hotel, store or restaurant they may want cash and pretend the card was rejected.

This is often very early in the morning or late at night when this person has no supevision.

,If you insert your debit card in a bank machine in Europe and remember your 4 digit PIN, it works close to 100%.

,Historically, first came American Express, then Master Card, then VISA- so in terms of recognition and common use, some places do not know how to process VISA.

,There are more European credit card systems that are compatible with MC.

,In the US you can go to a store, insert your card with a chip, and you are done.

In Europe you often have to insert the PIN number as well.

,American Express went from the most popular to the least, mostly because of errors at the company.

Special status American Express cards were a good idea as long as there were large American Express travel offices all over Europe, now they are counter-productive.