Perimeter of a Rectangle
Total length around a rectangle.
Formula
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Example
l=6, w=4 → P = 20
How it works
A rectangle has two pairs of equal sides: two lengths and two widths. To find the distance around it, you add all four sides, which gives l + w + l + w, and this simplifies to 2(l + w). The factor of 2 appears because each side length is counted twice.
When to use it
Use this formula whenever you need the distance around a rectangular shape, such as fencing a garden, framing a picture, or calculating trim around a room. It is also useful in geometry problems that ask for the boundary of a rectangle.
Worked example, step by step
Suppose a rectangle has length 9 cm and width 3 cm. P = 2(l + w) P = 2(9 + 3) P = 2(12) P = 24 cm So, the perimeter is 24 cm.
Common mistakes to avoid
- Adding only one length and one width instead of all four sides
- Using the formula for area, l × w, instead of perimeter
- Forgetting to include units in the final answer
Did You Know?
Of all rectangles with the same perimeter, the square is always the roomiest.
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