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A rectangle is a special quadrilateral with equal and 90-degree angles, parallel and equal opposite sides. This makes calculating the perimeter of a rectangle easy to learn and remember. If you've forgotten the formula for calculating the perimeter of a rectangle, check out the article below.
How to calculate the perimeter of a rectangle, various problem types, and illustrated examples.
I. Formula for Calculating the Perimeter of a Rectangle.
II. Illustrated Examples of Calculating the Perimeter of a Rectangle.
1. Calculate the perimeter of a rectangle when width and length are known.
2. Calculate the perimeter of a rectangle when the ratio and difference between length and width are known.
3. Calculate the perimeter of a rectangle when the area is known.
I. Formula for Calculating the Perimeter of a Rectangle
Consider the rectangle ABCD below with length a and width b
We will have the formula for the perimeter of a rectangle as follows
Introduction:
+ P represents the perimeter of a rectangle
+ AB, BC are the adjacent sides of the rectangle.
II. Illustrated Examples of Calculating the Perimeter of a Rectangle
Below are exercises applying knowledge of rectangle perimeter from basic to advanced. Although there are numerous examples, this article will present the most typical ones to help students approach various exercise types.
1. Exercise: Calculate the perimeter of a rectangle given the width and length
Example 1: Find the perimeter of rectangle ABCD when a = 20cm and b = 15cm
- Solution: Applying the formula for rectangle perimeter mentioned above, we get
So, the perimeter of rectangle ABCD will be: 70cm
Similarly, students can apply the above formula to solve an example of calculating the perimeter of a rectangle with a length of 25 cm and a width of 15 cm (answer: 80 cm)
2. Exercise: Calculate the perimeter of a rectangle given the ratio and difference between length and width
Solution Method: Solving problems using the difference-ratio method:
- Summarize the problem with a line segment diagram (segments that need to be equal)
- Find the difference of the segments according to the diagram
- Find the smaller number (width) by dividing the difference by the equal segment difference, then multiply by the segment number of the smaller number
- Find the larger number (length) by multiplying the width by 2 (because the length is twice the width)
* Apply the formula for calculating the perimeter of a rectangle: P = (a + b) x 2.
Example 2: Calculate the perimeter of a rectangle given that the length is twice the width and exceeds the width by 15m;
We have the diagram:
According to the diagram, the difference in equal segments is:
2 - 1 = 1 (segment)
Width of the land plot is
15 : 1 x 1 = 15 (m)
Length of the land plot is:
15 x 2 = 30 (m)
Perimeter of the land plot is:
(30 + 15) x 2 = 90 (m)
Answer: 90 m.
Answer: Width: 15m, length: 30m, perimeter: 90 (m)
Example 3: Calculate the perimeter of a rectangle knowing that the length is 3/2 times the width and exceeds the width by 10m
Answer: The length of the rectangle is 30m, the width is 20m, and the perimeter of the rectangle is 100
3. Calculate the Perimeter of a Rectangle with Known Area, Length, or Width
Solution Method:
To solve exercises of this type, students need to apply the formula for the area of a rectangle S(ABCD)= 2.a.b and the perimeter of a rectangle P = 2.(a+b)
Example 4: Calculate the perimeter of a rectangle with an area of 36 square cm and a width of 6cm
Answer: The perimeter of the rectangle is 24cm
Above are the formulas for calculating the perimeter of a rectangle and illustrated examples. Hopefully, with this article, you will find it easy to apply the formulas and calculate the perimeter of a rectangle to solve the problems you encounter.
A parallelogram is also a special quadrilateral; we can consider a rectangle as a special parallelogram. Therefore, the formula for calculating the perimeter of a parallelogram is similar to calculating the perimeter of a rectangle.
