Cross Math is a number puzzle where a set of tiles representing numbers (integers from 1-99) and mathematical symbols (operators +,-,×,÷ or =) must be placed into a crossword-style grid to form valid sums.

Touch and drag the blue tiles to place them into empty squares on the grid. If a tile is dragged to a valid location it will snap into place and turn gray. Any placed tile can be picked up and repositioned (either to another square on the grid or into the empty space surrounding the grid by dragging it again.

At the start of the puzzle some numbers and symbols will already be in place on the grid. These cannot be moved.

Important note: Completed sums entered into the grid are always read from left-to-right and from top-to-bottom. A subtraction or division sum that is only valid when read in the 'reverse' direction will need to have it's tiles re-arranged before it will be counted as valid by the game.

Two numbers or symbols cannot be placed in adjacent squares on the grid - each clue of the crossword must contain a valid equation starting and ending with a number, and alternating between numbers and operators in it's body. Each sum must contain an "=" symbol to be valid.

Each sum will always be in the format:

[ Number ] [ = ] [ Number ] [ +,-,×,÷ ] [ Number ]

-or-

[ Number ] [ +,-,×,÷ ] [ Number ] [ = ] [ Number ]

If a mathematically valid sum is entered on the grid, the symbols on those tiles will turn green. Please note that this only indicates that the sum itself is correct - it may not fit with the surrounding sums. You can still move and replace the tiles if you need to do so.

If an incorrect sum is entered into the grid, the symbols on those tiles will turn red. You can remove the tiles again to correct the error. (Don't forget that sums are read in a fixed direction as described above.)

Once all the tiles have been inserted into the grid in valid (green) sums, the puzzle is complete.

If you're stuck on a Cross Math puzzle, you can use coins to buy hints.

Hints can be used by tapping on the relevant icon in the status bar area at the top of the screen.

The cost (in coins) to use each hint is printed under its icon.

■ Place Some Tiles

Use this hint to automatically move a few tiles to their correct locations on the grid. Those tiles will then be fixed in place.

■ Check For Errors

Use this hint to scan the grid for incorrectly placed tiles. Any that are found will be highlighted in red, allowing you to remove them or reposition them on the grid.