Unlocking the secret in product codes
Arnold's Challenges

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!

Challenges

Challenge #1

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).

Correct! Great work!
Sorry, that is incorrect.
Please enter an answer.

Challenge #2

What is the check digit that’s missing from this 12-digit product code? 7 19821 37345 _

Correct! Great work!
Sorry, that is incorrect.
Please enter an answer.

Challenge #3

What is the check digit that’s missing from this 13-digit product code? 9 300652 80460_

Correct! Great work!
Sorry, that is incorrect.
Please enter an answer.

Challenge #4

The first digit on this product is missing - can you work out what it is?

A thirteen digit product code with the first digit missing. The rest of the digits are 400547010059.
Correct! Great work!
Sorry, that is incorrect.
Please enter an answer.

Challenge #5

The second digit on this product is missing - can you work out what it is?

A thirteen digit product code with the second digit missing. The digits are 9, followed by the smudged digit, followed by 00657233860.
Correct! Great work!
Sorry, that is incorrect.
Please enter an answer.