//I don't remember learning any of the above in school but that was around 35-40 years ago.//
No you wouldn’t, Tigger. But you were taught how to add up, subtract, multiply and divide, which of those was appropriate to what you wanted to do and which order to do them in.
//5p//
Correct. Method: deduct the “excess” from the total; divide what’s left by 2 and that’s the cost of the cheapest item. This is not really maths. The only arithmetic involved is taking £1 away from £1.10 and dividing 10 by 2. But it demonstrates perfectly that having a calculator will not solve everything. I solved such puzzles at primary school. We called them “problems.”
I have ‘A’ Level maths (‘B’ Grade). I passed when an ‘A’ Level was an ‘A’ Level (rather than now, where they appear to be 'O' Levels which take two years longer to gain than mine did). I have a better understanding of maths than my nephew who gained a 2:1 in Physics fifteen years ago. He has ‘A’ Level maths but his competence in the subject is not really much better than mine was at ‘O’ Level. But then I went to a grammar school and he didn’t (because there were none where he lived).
Many people I encounter are “astonished” that I can add up two or three sums of money in my head. They are only astonished because it has never occurred to them to learn how to do so and they’ve never been encouraged to try. But this isn’t maths. This is arithmetic and it is woefully lacking in large numbers of people under about sixty.
Mr Sunak could keep pupils in school learning Maths until they are 88. It would make no difference to their competence in the subject.