Henry Ernest Dudeney/Modern Puzzles/39 - The Two Trains

Modern Puzzles by Henry Ernest Dudeney: $39$

The Two Trains

Two railway trains, one $400$ feet long and the other $200$ feet long, ran on parallel rails.

It was found that when they went in opposite directions they passed each other in $5$ seconds,

but when they ran in the same direction the faster train would pass the other in $15$ seconds.

Now, a curious passenger worked out from these facts the rate per hour at which each train ran.

Can the reader discover the correct answer?

Of course, each train ran with a uniform velocity.

Sources

• 1926: Henry Ernest Dudeney: Modern Puzzles ... (previous) ... (next): Arithmetical and Algebraical Problems: Locomotion and Speed Puzzles: $39$. -- The Two Trains
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Arithmetical and Algebraical Problems: Speed & Distance Puzzles: $67$. The Two Trains