I think I could work out the length of the train in km and therefore how long it takes to pass a point given its speed in kph. Then the same with the other train. But I can't figure out how I work out how long it takes them to pass each other. If you have time, I am intrigued how it works! - ThreadSky

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oddthisday.bsky.social • 4 days ago

I think I could work out the length of the train in km and therefore how long it takes to pass a point given its speed in kph. Then the same with the other train. But I can't figure out how I work out how long it takes them to pass each other. If you have time, I am intrigued how it works!

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rfbooth.bsky.social•4 days ago

Oh, I meant the geometry problem! But I would be able to do the train, I shall return 🤞

oddthisday.bsky.social•4 days ago

Intrigued by both, tbh!

rfbooth.bsky.social•4 days ago

Here’s the other one. The key fact is, if you move one point of a triangle parallel to its opposite side, the area doesn’t change. So the triangle transforms twice to be half the medium square, that is ten (since the medium square is four small squares).

rfbooth.bsky.social•4 days ago

Ok, each train is 48m long. We can imagine one is still and the other is moving at 55kph. 55kph is 55000/3600 = 275/18 m/s.

The moving train needs to cover 96m, half to get alongside and the other half to get clear. 96÷(275/18)=6.28 seconds..

oddthisday.bsky.social•4 days ago

This is fascinating, thank you. The calculations are fairly simple, really - it was the assuming one train is still and the other moving at the combined speed that stumped me (plus the bit about combining the lengths. It was always a simple step I couldn't see with maths!)

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