Every cell gets a number: in a 3x3 grid these are the numbers 1, 2 and 3, in a 4x4 grid the numbers 1 to 4.
In every row and every column each number may appear only once.
The thickly outlined cells are called cages; the small number in the corner tells you what the numbers in this cage have to add up to.
You always count with plus, never with minus. Write the numbers into the cells.
Example
For parents
What does this exercise practice?
Number cages practices adding and trains logical thinking, because every number has to fit its row, its column and its cage.
Common pitfalls
Many children only check the cage and forget the row and column. It helps to first work out all the cages and then look whether each number appears only once in its row and column.
How to practice at home
Draw a grid on paper and fill it with coins or building blocks, one piece for each number. Check the rule: in every row and column each piece may lie only once.