Trade Math · Perimeter
Perimeter of shapes and objects
Perimeter is the distance around the outside of a shape. It's how you order baseboard, fencing, pipe to trim a room. Easier than area: no multiplication of dimensions, but the quick-glance mistakes are expensive.
Cheat sheet
- Rectangle: P = 2(L + W), or just add all four sides.
- Triangle: P = side1 + side2 + side3
- Regular polygon (all sides equal): P = number of sides × side length
- Circle (circumference): C = 2 × π × r or π × d (π ≈ 3.14)
- Composite / irregular: add every segment of the outer boundary: don't skip the short ones.
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