Decoders · difficulty 2 of 3
NHS number checksum 🏥
An NHS number is ten digits. Weight the first nine by 10 down to 2, take 11 minus the remainder mod 11, and that is the tenth digit. A result of 10 means the number is invalid.
This one is part of Pro. Plenty of arcade challenges are free to play right now.
Skills: strings, maths, dicts