4th Grade Area and Perimeter of Rectangles Lesson (Free PDF)
Area is the number of unit squares that cover a flat shape, and perimeter is the distance around it. For a rectangle, area = length × width and perimeter = 2 × length + 2 × width. A rectangle 8 feet long and 3 feet wide has an area of 24 square feet and a perimeter of 22 feet.
Grade 4 · Common Core State Standards: 4.MD.A.3
- Area of a rectangle = length × width, measured in square units.
- Perimeter of a rectangle = 2 × length + 2 × width, measured in plain units.
- A square is a rectangle whose four sides are equal.
- If you know the area and one side, divide to find the other side.
- Area tells how much to cover; perimeter tells how far around.
What is the area of a rectangle?
Area tells how much flat space a shape covers. We count unit squares, like floor tiles. This rectangle has 6 squares in every row and 4 rows, so it has 24 squares.
\(A = l \times w\) where l is the length and w is the width. Area is measured in square units, such as square feet (sq ft) or square inches (sq in).
What is the perimeter of a rectangle?
Perimeter is the distance around the outside edge. Imagine walking along a fence. A rectangle has two long sides and two short sides, so add them all.
\(P = 2 \times l + 2 \times w\) or \(P = 2 \times (l + w)\). Perimeter is measured in plain units, such as feet or inches.
How do you find a missing side of a rectangle?
Area is length times width, so use division to undo it. If a rectangle has an area of 48 square feet and a length of 8 feet, then the width is \(48 \div 8 = 6\) feet.
How do you solve an area or perimeter word problem?
First decide what the question needs. A fence, a border, or a ribbon around something means perimeter. Carpet, paint, or grass covering something means area.
Example. Maya’s garden is 9 ft long and 5 ft wide. How much fence goes around it, and how much soil covers it?
- Fence is around the edge, so find the perimeter: \(2 \times 9 + 2 \times 5 = 18 + 10 = 28\) ft.
- Soil covers the garden, so find the area: \(9 \times 5 = 45\) square feet.
- Write the units: 28 ft of fence and 45 sq ft of soil.
Questions about area and perimeter of rectangles
What is the difference between area and perimeter?
Perimeter is the distance around a shape, so you add the side lengths. Area is the amount of space inside a shape, so you multiply length by width.
Why is area measured in square units?
Area counts squares that fit inside a shape. A square foot is a square that is 1 foot on each side, so the area of a floor is written in square feet.
How do you find the perimeter of a square?
A square has four equal sides, so multiply one side by 4. A square with sides of 6 inches has a perimeter of 4 × 6 = 24 inches.
How do you find a missing width when you know the perimeter?
Subtract the two known lengths from the perimeter, then divide by 2. If P = 30 in and the length is 9 in, then 30 – 18 = 12 and 12 ÷ 2 = 6 in.
Can two rectangles have the same perimeter but different areas?
Yes. A 7 ft by 3 ft rectangle and a 5 ft by 5 ft rectangle both have a perimeter of 20 ft, but their areas are 21 sq ft and 25 sq ft.
All Grade 4 chapters: Grade 4 math.
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