Riding faster gets him there an hour early. Riding slower, an hour late
Sir Edwyn de Tudor must reach a castle by exactly five o'clock. Riding at a steady 15 miles an hour, he works out he'd arrive a full hour before his deadline. Riding at a steady 10 miles an hour instead, he'd arrive a full hour after it. How far away is the castle, and at what steady speed would get him there at exactly five o'clock?
Reveal the answer
The castle is 60 miles away, and riding at exactly 12 miles an hour gets him there precisely on time. Henry Dudeney published this as 'Sir Edwyn de Tudor' in Amusements in Mathematics (1917).
— Henry Ernest Dudeney, Amusements in Mathematics — Thomas Nelson & Sons, 1917
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