Addition Equation Sudoku
You need to find the values of the stars before you can apply normal Sudoku rules.
Age
11 to 14
Challenge level
By Henry Kwok
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Rules of Addition Equation Sudoku
Like the standard sudoku, this sudoku has the basic rule:
- Every row, every column and every 3x3 box in the grids contains the digits 1 through 9.
The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the 9x9 grid. At the bottom and right side of the 9x9 grid are numbers, each of which is the sum of a column or row of unknown digits marked by asterisks.
In this puzzle, a set of 17 equations can be formed from the columns and rows of unknown digits and constants. For example, in the fourth and fifth columns beginning from the left of the 9x9 grid, the following equations can be formed:
$* + * + * = 6$ and
$* + * = 9$.
In the eighth and ninth rows beginning from the top of the 9x9 grid, the following equations can be formed:
$* + * + * = 11$ and
$* + * = 13$.
After solving all the equations, the puzzle is solved by the usual sudoku technique and strategy.
A printable version of the problem can be found here.
Caitlin kept a record of the order in which she filled the Sudoku.
She filled the cell marked 1 first, then the cell marked 2, then the cell marked 3...
You might like to retrace her route to fill in the cells in the same order, though this is just one possible route through the problem.
You can print her journey here.
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