Brainteaser 1730: Not so usual

From The Sunday Times, 12th November 1995 [link]

As usual Eric was early for his morning train. Two express trains of the same length passed through the station in opposite directions, each at its own constant speed. Out of interest Eric timed them and noted that the faster one took 6 seconds to pass him, while the slower one took 8 seconds.

As soon as they had passed he saw his travelling companion, Len, 30 yards along the platform. In his conversation later, Eric told Len that he had been standing exactly in line with the point at which the fronts of the trains coincided.

Len then commented that, by coincidence, he had been standing exactly in line with the point at which the ends of the trains coincided. Eric was delighted because he was now able to work out the speeds of the trains.

How long were the trains?

This puzzle was included in the book Brainteasers (2002, edited by Victor Bryant), under the title of “Commuter computer”. The puzzle text above is taken from the book.

[teaser1730]