I am not sure if I would have been able to work it out on the spur of the moment in an exam. A bit like a clue in a cryptic crossword - the solution might occur at once, later ... or not at all.
Another item in the same episode of Radio 4's More or Less (June 5) discussed Maths as a 'stress subject'. It asked the question whether better outcomes for students might be achieved if Maths were more coached more like a leisure sport - and less presented as a hard drill, which can make learners feel 'bad' about getting things wrong.
Of course there will always be those for whom, whatever the method and means of presentation, Maths (or another subject) will yield no enjoyment and have no fascination. Such is the predicament of the suffering 'little Hanno' (whose only talent is for music) in Thomas Mann's novel of 19th Century Germany, Buddenbrooks:
It was the summer holidays, but little Hanno had private lessons in arithmetic, in order to keep up with his class. Somewhere out in the suburb ... in a little ill-smelling room, a man in a red beard, with dirty fingernails, was waiting to discipline him in the detested 'tables'.
One can always to do something about the ill-smelling room and the fingernails, but the tables, alas, the tables are a fixture.