Number Puzzles
Fifty classic puzzles, with worked solutions
2026 · 56 pp
Fifty classical number puzzles, re-authored in contemporary language and given fresh, fully worked solutions, the suppressed digit and casting out nines, the taxicab number 1729, square palindromes and figurate numbers, anomalous cancellation, automorphic and self-describing numbers, the coconut Diophantine, Ramanujan's house number, the only magic hexagon, the eight queens, and more.
A small collection of classic number puzzles, the kind that have circulated for a century or more in magazines, common rooms and the backs of notebooks. Each has been chosen for one reason: that it hides a genuinely pretty piece of reasoning, and rewards you the moment you see it.
Fifty puzzles, each its own short piece. The statement comes first, set in plain modern language, and the solution follows at once, worked through in full rather than merely announced. Among them: the suppressed-digit trick and why nine governs it; the taxicab number 1729; the only magic hexagon that exists; the eight queens; factorions like 145 and 40585; the automorphic numbers 376 and 625; the coconut-and-monkey Diophantine; Ramanujan’s house number; counting in threes with four weights; and the largest postage you cannot make from two stamps.
Nothing here asks for mathematics beyond school. A reader comfortable with ordinary arithmetic, a little algebra and the patience to follow a clear chain of reasoning will be able to read every solution to the end. Where a puzzle turns on a single idea, casting out nines, a difference of two squares, balanced ternary, the idea is named and explained, so the same trick is yours to use again. Cover the solution, attempt the puzzle, and consult the working only when you are ready.
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