Skill: Find area by counting square units

Area tells how much space is covered inside a flat shape. We measure area in square units. Each small square counts as $1$ square unit.

Suppose a rectangle is made of this grid:

$$\begin{array}{|c|c|c|} \hline \Box & \Box & \Box\\ \hline \Box & \Box & \Box\\ \hline \Box & \Box & \Box\\ \hline \Box & \Box & \Box\\ \hline \end{array}$$

Step 1: Count the rows.
There are $4$ rows of squares.

Step 2: Count the squares in each row.
Each row has $3$ squares.

Step 3: Count all the squares.
There are $4$ groups of $3$:

$$3+3+3+3=12$$

So, the area of the rectangle is:

$$\boxed{12\text{ square units}}$$

Remember: area counts the squares inside the shape. Perimeter counts the distance around the outside.