Skill: Decompose shapes mentally

Look at the whole shape and imagine lines that split it into familiar pieces, such as squares or rectangles. The pieces do not have to stay in the same direction.

Imagine this shape made from equal squares:

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Step 1: Find a familiar part.
The top part is a rectangle that is $3$ squares across and $2$ squares down:

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Step 2: Find what is left.
The remaining part is a tall rectangle made from $2$ squares:

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So the whole shape can be thought of as one rectangle and one smaller rectangle.

Step 3: Picture the pieces moving.
Imagine lifting the tall rectangle, turning it sideways, and placing it next to the larger rectangle. Even though its direction changes, it is still the same rectangle.

Step 4: Put the pieces back.
Place the two pieces in their original positions. Together, they make the whole shape again.

When you see a new shape, ask yourself: “Where could I imagine a straight line that would split this into familiar shapes?”