This is a fairly random collection of puzzles, mostly with a mathematical flavour. A few are original, but most are picked up from friends, books, newsgroups, etc. Some are credited [like this], but in many cases I'm afraid I've forgotten where they came from. Some aren't really puzzles, but just questions that happen to have caught my interest.

Many of them have a "spoiler" version giving the answer, or a partial
answer, and usually some working. Except where credited most of the
solutions are by me, in the sense that the working's mine even if they'd
been solved by others before. This means there may well be errors in the
working. The symbol ??? indicates a puzzle
to (part of) which I don't know the answer. The notation
`M`e`N` means `M` x
10^{N}.

If you make any progress on any of these puzzles, or if you'd like to contribute a new one, then please do tell me about it.

- Miscellaneous pure mathematics
- Game theory and probability
- Geometry and topology
- Bridging a river with unit rods
- Fly on 2 x 1 x 1 brick --- spoiler
- Lawnmower --- spoiler
- Offball: object whose projections are disks --- spoiler
- Paper-folding
- Platonic solids inside and outside a unit sphere --- spoiler
- Portion of planets from which others are invisible --- spoiler
- Sofas and ladders round corners --- spoiler
- Sphere packings --- spoiler
- Sunrise in the west --- spoiler

- Physics and real-world
- Large and small numbers

This page is maintained by Thomas Bending,
and was last modified on Sat 23 Jan 2021.

Comments, criticisms and suggestions are welcome.
Copyright © Thomas Bending 2021