Introduction to perimeter | Measurement | Pre-Algebra | Khan Academy

TL;DR

Perimeter is the length of the boundary of a figure, and it is calculated by adding the lengths of all of its sides.

Transcript

When people use the word "perimeter" in everyday language, they're talking about the boundary of some area. And when we talk about perimeter in math, we're talking about a related idea. But now we're not just talking about the boundary. We're actually talking about the length of the boundary. How far do you have to go around the boundary to essenti... Read More

Key Insights

• 💠 Perimeter in mathematics refers to the length of the boundary of a shape or figure.
• 💠 Perimeter is calculated by adding up the lengths of all the sides of a shape.
• 🙃 Perimeter is measured in the same units as the lengths of the sides.
• 💠 If the sides of a shape are equal, the perimeter can be found by multiplying the length of one side by the number of sides.
• 🙃 Irregular polygons also have perimeters that can be calculated by adding up the lengths of their sides.
• ❓ Perimeter is a fundamental concept in geometry.
• 💁 The perimeter of a shape provides important information about its size and the distance required to go around it.

Questions & Answers

Q: What is perimeter?

Perimeter refers to the length of the boundary of a shape. It is the total distance required to go completely around the shape and is measured in the same units as the lengths of the sides.

Q: How do you calculate the perimeter of a triangle with equal sides?

If a triangle has equal sides, the perimeter can be calculated by multiplying the length of one side by the number of sides. For example, if each side of the triangle is 4 feet, the perimeter would be 4 feet plus 4 feet plus 4 feet, which equals 12 feet.

Q: How is the perimeter of a rectangle calculated?

To calculate the perimeter of a rectangle, add up the lengths of all four sides. For example, if the lengths of the four sides are 3 meters, 5 meters, 3 meters, and 5 meters, the perimeter would be 3 meters plus 5 meters plus 3 meters plus 5 meters, which equals 16 meters.

Q: How do you calculate the perimeter of an irregular polygon?

To calculate the perimeter of an irregular polygon, add up the lengths of all its sides. There is no specific formula for irregular polygons. For example, if the sides of an irregular polygon are 1 unit, 4 units, 2 units, 2 units, 4 units, and 6 units, the perimeter would be 1 unit plus 4 units plus 2 units plus 2 units plus 4 units plus 6 units, which equals 19 units.

Summary & Key Takeaways

• Perimeter refers to the length of the boundary of a shape.

• To calculate the perimeter of a shape, add up the lengths of all its sides.

• Perimeter is measured in the same units as the lengths of the sides.