MathematicsBarcodes contain a checksum an ingenious use of mathematics that even lends itself to a fun way to surprise your friends, says Katie Steckles 5 February 2025 Shutterstock/Scott RothsteinSometimes there are hidden patterns in numbers you might not immediately notice. One example of this is in barcodes, the sequences of digits we use to identify products.Try it yourself find an object with a 13-digit barcode. (If you are in the US, a 12-digit barcode will also work, if you imagine an extra 0 on the front of it.) Books wont work, since they use a slightly different system, but magazines do, so you can use a copy of New Scientist. Add together the first, third, and fifth digits and so on, to get the sum of