Here are five challenges that build on the ideas you’ve been working with. You might like to do one a day... The first one of each set should be fairly easy, but they get harder. What do you get out of this? Just the warm feeling you get when you know you've solved one of Arnold's challenges, and the satisfaction of knowing that you've mastered a deep idea from computer science.
Enjoy the challenges!
If a product scans with the 13-digit code 9 414942 119252, is it likely to have been scanned correctly? (Type in yes or no).
What is the check digit that’s missing from this 12-digit product code? 7 19821 37345 _
What is the check digit that’s missing from this 13-digit product code? 9 300652 80460_
The first digit on this product is smudged - can you work out what it is?
The second digit on this product is smudged - can you work out what it is?