Barcode: the last digit

Python Intermediate alien ages 11-13 From CS Unplugged

The problem

A 13-digit barcode ends in a check digit. Write a function barcode_check_digit(first12) that gets the first 12 digits as text and gives back the last digit as a number. How: add the digits, but multiply every second one (the 2nd, 4th, 6th ...) by 3. The check digit is (10 - total % 10) % 10.

You will practice: check digits, loops, remainder (%)

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CC BY-SA 4.0

Adapted from a CS Unplugged programming challenge by the University of Canterbury Computer Science Education Research Group, licensed CC BY-SA 4.0.

Original challenge · License: CC BY-SA 4.0

Changes: Rewritten in our own words as a function with tests, hints and steps, in Python and JavaScript, by Open Cosmos. This version is also CC BY-SA 4.0.