Area and Perimeter of Rectangles
Aligned to 4.MD.A.3 — Common Core State Standards for Mathematics.
What this lesson teaches
Perimeter is the distance all the way around a rectangle: add up all four sides. Area is the space inside: multiply length times width. Perimeter is measured in units; area is measured in square units.
Worked examples
Example 1
A rectangle is 8 cm long and 5 cm wide. Perimeter: 8 + 5 + 8 + 5 = 26 cm. Area: length times width = 8 x 5 = 40 square cm.
Example 2
A room is 12 ft by 10 ft. Area: 12 × 10 = 120 square feet of carpet. Perimeter: 12+10+12+10 = 44 feet of baseboard.
Example 3
If you know the area is 48 square feet and one side is 6 feet, work backwards: 48 ÷ 6 = 8, so the other side is 8 feet.
Practice questions
- Find the perimeter and area of a rectangle 7 m by 4 m.
- A rectangle has an area of 24 square feet and a length of 6 feet. What is its width?
- A garden is 10 ft by 3 ft. How much fence is needed to go around it?
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Area y perimetro de rectangulos
El perimetro es la distancia alrededor de un rectangulo: suma los cuatro lados. El area es el espacio interior: multiplica largo por ancho. El perimetro se mide en unidades; el area se mide en unidades cuadradas.
Ejemplo 1: Un rectangulo mide 8 cm de largo y 5 cm de ancho. Perimetro: 8 + 5 + 8 + 5 = 26 cm. Area: largo por ancho = 8 x 5 = 40 cm cuadrados.
Ejemplo 2: Un cuarto mide 12 ft por 10 ft. Área: 12 × 10 = 120 pies cuadrados de alfombra. Perímetro: 12+10+12+10 = 44 pies de zoclo.
Ejemplo 3: Si sabes que el área es 48 pies cuadrados y un lado mide 6 pies, trabaja al revés: 48 ÷ 6 = 8, así que el otro lado mide 8 pies.
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