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Last updated on September 26, 2025
The perimeter of a shape is the total length of its boundary. For complex shapes, the perimeter is found by summing the lengths of all individual segments that make up the shape's boundary. Perimeter is commonly used in various applications like fencing, sewing, and construction. In this topic, we will explore how to calculate the perimeter of complex shapes.
The perimeter of a complex shape is the total length of all its boundary segments. By adding the lengths of each segment, we arrive at the shape's perimeter.
For example, consider a complex shape that consists of a rectangle with dimensions 8 cm by 5 cm and a semicircle with a radius of 4 cm attached to one of its shorter sides. The perimeter would be the sum of the perimeter of the rectangle and the curved part of the semicircle.
Let's consider another complex shape example: a rectangle with a length of 12 cm and a width of 6 cm, combined with a quarter circle with a radius of 6 cm attached to one of the rectangle's corners.
To find the perimeter, calculate the perimeter of the rectangle and add the curved edge of the quarter circle.
To find the perimeter of complex shapes, apply the relevant formulas for each individual shape component and sum their perimeters.
For instance, consider a shape made up of a square with sides of 5 meters and a semicircle on one side with a radius of 2.5 meters. First, calculate the perimeter of the square and then add the curved part of the semicircle. Example Problem on Perimeter of Complex Shapes
For finding the perimeter of a complex shape, break down the shape into simple components, calculate each perimeter, and sum them.
For example, a composite shape consists of a triangle with sides of 3 cm, 4 cm, and 5 cm, and a semicircle with a diameter of 5 cm.
Calculate the perimeter of the triangle and add the curved edge of the semicircle.
Learning some tips can simplify the calculation of the perimeter for complex shapes.
Here are a few tips and tricks:
While calculating the perimeter of complex shapes, one may encounter errors or difficulties. Here are some common mistakes and how to avoid them:
A garden path is designed in the shape of a rectangle measuring 20 meters by 10 meters with a semicircle at one end. Calculate the total perimeter of the path.
74.28 meters
The perimeter of the rectangle is 2(l + w) = 2(20 + 10) = 60 meters.
The perimeter of the semicircle is πr = π(5) = 15.7 meters.
Total perimeter = 60 + 15.7 - 10 = 65.7 meters.
(Subtract 10 meters for the diameter shared by the rectangle and semicircle.)
A racetrack has the shape of a rectangle 100 meters long and 50 meters wide, with semi-circular ends. Find the total perimeter of the racetrack.
400 meters
The straight edges of the racetrack are the length of the rectangle: 100 meters each.
The semi-circular ends have a diameter of 50 meters, thus circumference of each semicircle = πr = π(25) = 78.54 meters.
Total perimeter = 200 + 78.54 + 78.54 = 357.08 meters.
Find the perimeter of an L-shaped figure composed of two rectangles, one measuring 4 cm by 3 cm and the other 5 cm by 2 cm, joined along a 2 cm side.
28 cm
Total perimeter = (4 + 3 + 5 + 2 + 3 + 2 + 5) - 2 = 22 cm.
(Subtract the 2 cm where the rectangles are joined since it’s counted twice.)
A swimming pool is in the shape of a rectangle with a length of 25 meters and a width of 10 meters, with a circular spa of diameter 5 meters attached at one corner. Calculate the perimeter.
80.7 meters
Rectangle perimeter = 2(l + w) = 2(25 + 10) = 70 meters.
Circle perimeter = πd = π(5) = 15.7 meters.
Total perimeter = 70 + 15.7 - 5 = 80.7 meters.
An irregular park shape consists of a triangle with sides 8 meters, 10 meters, and 12 meters, with a semicircle of diameter 8 meters attached to one of the sides. Find the perimeter.
41.14 meters
Triangle perimeter = 8 + 10 + 12 = 30 meters.
Semicircle perimeter = πr = π(4) = 12.57 meters.
Total perimeter = 30 + 12.57 - 8 = 34.57 meters.
Seyed Ali Fathima S a math expert with nearly 5 years of experience as a math teacher. From an engineer to a math teacher, shows her passion for math and teaching. She is a calculator queen, who loves tables and she turns tables to puzzles and songs.
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