Find one unknown
Start with the equation that has the fewest empty cells. A line with one unknown gives you a forced value.
Free online number puzzle
Play cross math online
Place every number so all the crossing equations are true at once. Today's Lattice is free in your browser, needs no account, and is machine-proven to have exactly one solution.
7+5=12
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The puzzle in one minute
What is a cross-math puzzle?
Cross math—also written cross-math or described as a math crossword—is an arithmetic logic puzzle. Numbers sit in a connected grid, operators join them into equations, and a tile can belong to more than one equation. That crossing is the important part: a number that works across one line must also work down, diagonally, or along any other path touching the same cell.
You are not racing through isolated sums. You are using each solved equation as evidence for the next one, much as a letter in a crossword helps two words at once. The arithmetic is familiar; the challenge is seeing which fact forces the next placement.
Lattice rules
How to play cross math
- Use the number tray. Every movable tile belongs in one open cell. If a value appears twice in the tray, those are two separate tiles.
- Make every equation true. Follow the connected path to its equals sign and result. A crossing cell must satisfy every equation that touches it.
- Use standard order of operations. In Lattice, multiplication and division are evaluated before addition and subtraction. Division is exact; the game never rounds an answer to make a tile fit.
- Move only what is available. Printed givens stay fixed. You can place, move, or take back the tiles from the tray while you reason.
- Finish by deduction. Every shipped board has one verified solution, so trial and error is never required.
Other cross-math games sometimes calculate strictly left to right. Check their rules before solving; Lattice deliberately uses standard arithmetic precedence.
A repeatable strategy
How do you solve a cross-math puzzle?
Check the crossing
Before placing that value, confirm it also fits every other equation connected to the cell.
Follow the cascade
Re-read the equations touched by the new tile. One of them may now have a single unknown.
Eliminate, don't guess
Use factors, exact division, differences, and the remaining tray to rule candidates out.
Choose your next step
More cross-math help
Ready when you are
Start with today's proven puzzle
Play one board in the browser, use a hint if you need a nudge, and share a spoiler-free result when you finish.
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