The grid is split into rectangles without any leftovers. No square stays empty, and no two rectangles overlap.
Every rectangle holds exactly one number. It tells you how many squares the rectangle is made of.
So a 12 can be 2 · 6, 6 · 2, 3 · 4 or 4 · 3. The space in the grid decides which shape fits.
Start with the numbers that have only one single shape left. Draw the borders with a ruler.
Example
For parents
What does this exercise practice?
Shikaku makes factorisation visible. The child looks for all rectangles with a given area and notices that 12 is not just “twelve”, but also 3 · 4 and 2 · 6. Because the grid allows only one shape, memorising turns into choosing.
Common pitfalls
A rectangle may contain only one single number. Drawing a big rectangle around two numbers may give the right area, but it breaks the rule.
How to practice at home
Put twelve toy blocks on the table and build a rectangle from them. How many different rectangles are possible? Then try the same with 10, with 9 and with 7 blocks - with 7 only a single long row works.
Related: Times as a dot array, Continuing a tiling