"If you see this mentioned in the question, little alarm bells should be ringing." Words of wisdom from my then maths teacher sometime at the twilight of the 1980s. It related to solving particular kinds of maths questions, and he was fond of saying it. I have no recollection of what would be mentioned in the question, how these alarm bells would help you solve the question, or indeed the name of the teacher. Despite failing to remember any of the key guidance from this lesson, the concept of 'little alarm bells ringing' remains, testament to the lasting impact of seemingly fleeting moments; educational detritus.

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