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Who is the average person in the world, and what is their age, location, physical appearance etc?

Rachel Peynado,

Ashton-under-Lyne, Greater Manchester, UK

Are there limitless permutations of QR codes or are they recycled after a prescribed length of time?

Bonita Ely,

Sydney, Australia

To answer this question – or ask a new one – email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

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