In times of inflation - and there is a lot of it around just now - companies like to avoid price hikes. A favourite tactic is to reduce product size while keeping the price the same. But do you know how the maths works?

James Munro explains the mathematical cunning of shrinkflation, the first in a series of (very) short films about numeracy, a skill we all need to navigate our way around the world, but which we perhaps take for granted.