About Hourglass puzzles
Hourglass puzzles present two stacked triangles that share a waist, and the rule almost always describes a relationship *between* the halves rather than inside either one. The top might be the sum of the bottom, or the bottom might be the top reversed and reduced, or the waist might be the difference between the two outer rows. Reading the figure as two objects instead of one is the entire unlock.
These are the hardest puzzles on Numerly, and they are placed last for good reason: they assume you already look for rules rather than answers, that you test theories against multiple pieces of evidence, and that you are comfortable with two-step arithmetic. Solvers who arrive here after clearing the earlier worlds usually find them tough but fair. Solvers who jump straight in usually bounce.
The most productive question to ask is what the waist is doing. Because it belongs to both halves, it is the only number constrained twice, so any correct theory has to explain it from above and from below. Get the waist right and the rest of the figure tends to collapse into place in a few seconds.
If you want a single benchmark for how far your reasoning has come on Numerly, clear an hourglass pack without hints.
How to solve Hourglass
- Read the figure as two triangles that share the waist, not as one shape.
- Explain the waist from both halves — a correct rule satisfies it twice.
- Compare the totals of the top and bottom halves before testing anything finer.
Skill trained: Comparative reasoning between two related groups.