Understanding Perimeter

Perimeter is the total distance around a shape.

How to Find Perimeter

Add up all the side lengths!

Common Formulas

Rectangle

$P = 2l + 2w = 2(l + w)$

Where $l$ = length and $w$ = width

Example: Rectangle with length 8 and width 5 $P = 2(8) + 2(5) = 16 + 10 = 26$

Square

$P = 4s$

Where $s$ = side length

Example: Square with side 6 $P = 4(6) = 24$

Triangle

$P = a + b + c$

Just add all three sides!

Circle (Circumference)

$C = 2\pi r = \pi d$

Where $r$ = radius and $d$ = diameter

Example: Circle with radius 5 $C = 2\pi(5) = 10\pi \approx 31.4$

Real-World Applications

• Fencing: How much fence for a yard?
• Framing: Picture frame material needed
• Running: Distance around a track
• Borders: Trim around a room