Henry Ernest Dudeney/Modern Puzzles/43 - The Two Ships

Modern Puzzles by Henry Ernest Dudeney: $43$

The Two Ships

A correspondent asks the following question.

Two ships sail from one port to another -- $200$ nautical miles -- and return.

The Mary Jane travels outwards at $12$ miles an hour and returns at $8$ miles an hour,

thus taking $41 \tfrac 2 3$ hours on the double journey.

The Elizabeth Ann travels both ways at $10$ miles an hour, taking $40$ hours on the double journey.

Now, seeing that both ships travel at the average speed of $10$ miles per hour, why does the Mary Jane take longer than the Elizabeth Ann?

Perhaps the reader could explain this little paradox.

Sources

• 1926: Henry Ernest Dudeney: Modern Puzzles ... (previous) ... (next): Arithmetical and Algebraical Problems: Locomotion and Speed Puzzles: $43$. -- The Two Ships
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Arithmetical and Algebraical Problems: Speed & Distance Puzzles: $71$. The Two Ships