Attention Getting Question:
Before building a sandbox in your backyard, what would you need know? Knowing the perimeter and area would help you determine how much material you need to buy and how much space the sandbox will take up in your backyard.
What are perimeter and area? Perimeter and area are two ways to calculate the size of a shape. We’ll look specifically at each measurement.
Let’s start with perimeter. Perimeter is the distance around the outside of an object or shape. Think of perimeter as the outline or border around a shape. For example, this rectangular basketball court has lines going all the way around it. If a person were to walk all the way around the court, they would have walked the distance of the court’s perimeter. This fence is going around the perimeter of the square shaped garden. There is a border going around the perimeter of this triangular sign.
Distance, or length, is measured with linear units, such as centimeters, inches, feet, or even miles. To find the perimeter of a shape, add the length of all the sides.
This square has four equal sides. Each side is 8 meters long. To find the perimeter add 8 plus 8 plus 8 plus 8, or you can just multiply 8 times 4, because multiplication is really just repeated addition. 8 times 4 equals 32, so the perimeter is 32 meters.
Some odd shapes, like this one, have several sides. Add all of the sides to find the perimeter. This shape has seven sides. 8 plus 4 plus 5 plus 2 plus 3 plus 3 plus 5. The perimeter is 30 feet.
Knowing how to find perimeter can help you when finding how much border to put around a picture, how much fence to build around your yard, or the size of a rug to buy for a room.
Now let’s take a look at area. Area measures the size a surface takes up by determining the number of square units needed to cover the two-dimensional figure. What is a square unit? A square has four equal sides. All sides of this square are one centimeter long, so this is one square centimeter.
This whiteboard is five feet wide and three feet tall. If you divide it into square feet, you can find its area. Count the square feet. The area is 15 square feet.
What is the area of this shape? It is a little different because there are half squares in it. First, count the whole squares. There are 9 whole square units. Then count the half squares. Because two half square units equal one whole square unit. 9 plus 1 equals 10 square units.
Instead of counting the individual square units, you can calculate the area of rectangles and squares using the formula length times width. For example, this room is 10 feet wide and 9 feet long. Because it is a rectangle, multiply the length by the width to find the area. 10 feet times 9 feet equals 90 square feet.
Now that we know what perimeter and area are, we can build that sandbox. The sandbox will be 7 feet long and 4 feet wide. To find how much wood to buy to go around the outside, we can measure the perimeter. Add all four sides together: 7 feet plus 4 feet plus 7 feet plus 4 feet equals 22 feet. The perimeter of the box is 22 feet, so we would buy 22 feet of wood. We can multiply the length times the width to find out the area, or how much space the sandbox will take up in the backyard. Seven feet times 4 feet equals 28 square feet. The sandbox will take up 28 square feet in your backyard.
Perimeter and area are two ways to calculate shapes. Perimeter is the distance around the outside the shape. Find perimeter by adding the length of all sides. Area is the number of square units inside a shape. To find area, count the number of square units. If the shape is a rectangle or square, multiply the length times the width to find the area.