Homework.

I suppose it's normal for a father to help his son with homework; in this case, the son is 32¼ years old and his homework is school level maths. He's doing it as part of his second degree, where-as I left school at 16 and went straight into an apprenticeship. His excuse for needing help? It's 12 years since he left school and he's forgotten how to do it! I did point out to him how long it is since I left school.

This particular question concerns a train leaving London at 9:00 a.m. and arriving in Edinburgh at a specified later time; meanwhile, a second train leaves Edinburgh at 9:30 and duly arrives in London, again, at a set time. Assuming that they travel at constant speeds, at what time and place do their paths cross? Such answers as yesterday and next year both occurred; I think part of the problem was that he had one of them travelling back through time. If he can perfect the process, he should patent it.

I've just posted yesterday's, "Coming to an End."