IXL | Relationship between area and perimeter: find the area

The rectangles below have the same perimeter.

3 in

4 in

6 in

What is the area of the yellow rectangle?

square inches

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Learn with an example

question

The rectangles below have the same perimeter.

3 mm

4 mm

What is the area of the red rectangle?

square millimeters

key idea

Rectangles with the same perimeter can have different areas.

solution

Find the perimeter of the pink rectangle.

3 + 3 + 3 + 3 = 12

Both rectangles have a perimeter of 12 millimeters. Find the missing side length of the red rectangle.

You know that two sides of the red rectangle are 4 millimeters long. Subtract from the perimeter to find the combined length of the other two sides.

12 − 4 − 4 = 4

So, the combined length of the two other sides is 4. Divide by 2 to find the length of each of those sides.

4 ÷ 2 = 2

The red rectangle is 2 millimeters by 4 millimeters. Find its area.

2 × 4 = 8

The area of the red rectangle is 8 square millimeters.

Looking for more? Try these:

Lesson: Perimeter

Lesson: Area of rectangles

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Teacher tools

Work it out

Not feeling ready yet? These can help:

OO.10Find the area of rectangles and squares

OO.11Find the missing side length of a rectangle

Lesson: Perimeter

Lesson: Area of rectangles

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