To find the area of a rectangle, use the formula:

$\text{Area} = \text{Width} \times \text{Height}$

Given dimensions:

• Width = 800 mm
• Height = 400 mm

Step 1: Convert mm to square meters

Since 1 meter = 1000 mm, we convert:

• $800$ mm = $0.8$ m
• $400$ mm = $0.4$ m

Step 2: Calculate the area

$\text{Area} = 0.8 \times 0.4 = 0.32 \text{ m}^2$

Thus, the area of the rectangle is 0.32 square meters.

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Do you need further clarification? Here are some related questions:

1. What is the perimeter of the same rectangle?
2. How does the area change if the dimensions double?
3. How many such rectangles fit into a 10 m² surface?
4. Convert the area into square centimeters.
5. If this rectangle were a window, how much glass would be needed?

Tip: Always ensure that units are consistent before performing area calculations.