Friday 1 February 2019

Puzzle from A Beautiful Mind.

A classic puzzle to start our second series. It appears in the background of A Beautiful Mind and it is said that the famous mathematician John von Neumann immediately answered with the correct result. But we'll talk about solutions later!

Animation illustrating the problem courtesy of MathWorld.

Two trains are on the same track. They start 100km apart and head towards each other at a speed of 50km/h.

Whilst these two trains are heading for their collision a fly starts out on the front of one train and zooms directly to the front of the other at a speed of 75km/h (see the animation above). Once the fly reaches the second train it immediately darts back to the front of the first train at the same speed and repeats this back and forth motion until the two trains collide and the fly is squashed on impact.

How far has the fly traveled, before it meets its demise?

If you think you have the answer comment below, tweet it to us @PodcastMathsAt, or email us at

The answer will be posted next week.

No comments:

Post a Comment

Who are we?

Contact Form


Email *

Message *