Henry Ernest Dudeney/Modern Puzzles/38 - The Despatch-Rider

Modern Puzzles by Henry Ernest Dudeney: $38$

The Despatch-Rider

If an army $40$ miles long advances $40$ miles

while a despatch-rider gallops from the rear to the front,

delivers a despatch to the commanding general,

and returns to the rear,

how far has he to travel?

Sources

• 1926: Henry Ernest Dudeney: Modern Puzzles ... (previous) ... (next): Arithmetical and Algebraical Problems: Locomotion and Speed Puzzles: $38$. -- The Despatch-Rider
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Arithmetical and Algebraical Problems: Speed & Distance Puzzles: $66$. The Dispatch Rider