ratio-arithmetic
Which sun and ring take 3 planets
Every cell is a sun and a ring whose difference is even, so a whole planet fits between them and the drawing can be made. Shading is what happens when the second planet is asked for. Green assembles; grey fails the divisibility condition, which says the sun and ring teeth must add to a multiple of the planet count; pale fails the neighbour condition, where the planets would touch. Of 1251 cuttable designs, 417 — 33.3% — will actually take 3 equally spaced planets. The condition that removes most of them is arithmetic and appears in no drawing.
Where it is used
- Two inputs and one output More than one input
- Undercutting, and the seventeen-tooth rule Teeth
- The gearset that could not be assembled Drawn wrongly
- One wheel on ice More than one input
- A hundred to one from a difference of one More than one input
- Three mechanisms, one subtraction More than one input
- Which tooth meets which Teeth
- The reductions a planetary cannot give More than one input
- Two shafts that must be in line More than one input
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