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Cross Math Puzzle

Place the digits 1 to 9 so that three equations across and three down all come out right.

Type
Logic
Takes
about 2-5 min
Result in
seconds

Cross Math

~2-5 min

  1. Put the digits 1 to 9 into the grid, each one once.
  2. All three sums across and all three down must come out right.
  3. × and ÷ come before + and −, as on a calculator. Select a square, then tap a digit.

3 digits are given. Every puzzle has exactly one answer.

Your result: —

How it's measured

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How does a cross math puzzle work?

A cross math puzzle is a math crossword. Nine squares form three rows and three columns, with a sign between each pair and a total at the end of every row and column. Put each digit from 1 to 9 into one square so that all six equations come out right. 3 digits are given at the start; the other 6 wait in the tray.

Select an empty square and tap a digit, or type it. A total gets a tick when its equation is full and right, and turns red when it is full and wrong, so you always know which lines still need work.

Which order are the operations done in?

Multiplication and division come before addition and subtraction, as on a calculator and in school arithmetic. So 2 + 3 × 4 is 14, not 20. Signs of the same rank are worked from left to right: 8 ÷ 4 × 3 is 6, and 9 − 2 − 3 is 4. Every division in a puzzle comes out whole, and every total is between 0 and 99.

How is your Cross Math Puzzle time calculated?

Your result is the time from Start until all six equations are right. Next to it are your moves (each digit placed) and the hints you used (each places one digit, or fixes a wrong one). There is no Check button: the ticks already show which equations work. There is no rating either, because no published typical time exists for puzzles built like these.

How do you solve cross math puzzles?

  • Start with × and ÷. A product limits the digits a lot: a total of 72 from two multiplied digits can only be 8 × 9. A division needs a digit that divides evenly.
  • Use the given digits. A row with two digits known has only one value left to find, and the answer must be a digit not yet used.
  • Think about size. A small total with a × in it usually means a 1 or a 2 nearby; a large total with only + signs needs the big digits.
  • Each digit once. When a digit fits two equations, the crossing ones decide which; and the last digits in the tray often have only one home.

Is there only one answer?

Yes. A puzzle starts from a random order of the nine digits and random signs. Digits are then taken off the board one at a time, and one stays off only if every possible way of putting the missing digits back still leaves just one that makes all six equations right. The site's tests go further on a sample of puzzles and try all 362,880 orders of the nine digits: exactly one fits each time.

For quick arithmetic against the clock, try the Mental Math Test; for another number puzzle with sums, Kakuro.

Questions

Is a cross math puzzle the same as a math crossword?
Yes. Both names describe a grid of equations that cross, where one digit belongs to an equation across and another down.
Can a digit be used twice?
No. Each digit from 1 to 9 is used exactly once, so a digit already on the board is greyed out in the tray.
Why does 2 + 3 × 4 make 14?
Because multiplication comes before addition: 3 × 4 is 12, then 2 + 12 is 14. Every equation here follows that rule, as a calculator does.
Are negative totals possible?
No. Every total in these puzzles is between 0 and 99, and every division comes out whole.
What is a good time?
There is no published average for cross math puzzles of this design, so the page doesn't invent one. Compare your own times, and your moves, from one puzzle to the next.