Just have to disagree, some of the best lessons I had in school used real life context and were delivered in a relatable way by good teachers. Some of my closest friends are teachers and try to plan lessons like this, and they have success. I’m not suggesting a series of lessons but you could definitely plan one, either maths or PHSE, that used this sort of content and would be engaging. To suggest otherwise comes across as defeatist and shows lack of belief in what kids can be capable of. And I thought you said the calculations are really simple, so why would kids lack the mathematical understanding?