Puzzles
The Diesel Ship and the Seaplane
A diesel ship sets out on a long voyage. When it's 180 miles from shore, a seaplane — flying exactly ten times as fast as the ship travels — is sent out from shore to deliver the mail. How far from shore does the seaplane catch up with the ship?
Reveal the answer
200 miles from shore. If the ship's speed is v, by the time the seaplane (speed 10v) catches up, both have traveled for the same time t: the ship has gone 180+vt while the plane has gone 10vt, so vt=20 and the catch-up point is 10x20=200 miles out. From Boris Kordemsky's The Moscow Puzzles, the best-selling puzzle book in Soviet history.
— Boris Kordemsky, The Moscow Puzzles: 359 Mathematical Recreations — 1956 (English translation 1972, ed. Martin Gardner)
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