Bar Code Check Digit Trick

Bar codes have a pattern in their digits to help detect errors. A magic trick can be done where one person reads out all but the final digit on the bar code of a product, and the second person ‘predicts’ this final digit (the check digit) by using the pattern in the digits. Teach your class to do this trick and get them thinking about the maths that makes the trick work.

Equipment needed

Nothing special.

Curriculum Topics Covered

Multiples, following an algorithm, forming/solving simple equations.

More Information

See our Teacher Notes download for more information. The download Bar Code Trick Example gives an example that demonstrates the method for calculating the check digit, and the download Bar Code Trick Task Sheet contains activities for students. 

Also, you can see a younger version of Matt performing the trick at 3:43 in this YouTube video: