When it comes to figuring out perimeter and circumference, there are some important formulas that 7th graders should know. These formulas will help you not just in school, but also in everyday life!

Perimeter Formulas

1. Squares:

   • To find the perimeter of a square, you can use this simple formula: $P = 4s$ Here, $s$ is the length of one side.

2. Rectangles:

   • For rectangles, the formula is: $P = 2(l + w)$ In this formula, $l$ stands for the length and $w$ is the width.

3. Triangles:

   • To find the perimeter of a triangle, just add up all the sides: $P = a + b + c$ Here, $a$, $b$, and $c$ are the lengths of the sides.

4. Regular Polygons:

   • For any regular polygon, like a hexagon or a pentagon, you can use: $P = ns$ In this formula, $n$ is the number of sides and $s$ is the length of one side.

Circumference Formula

Circumference is a term we use for circles. Here’s how to find it:

1. Circles:
   • To calculate the circumference, you can use this formula: $C = \pi d$ Or, you can also use: $C = 2\pi r$ In these formulas, $d$ is the diameter (the distance across the circle) and $r$ is the radius (the distance from the center to the edge).

Tips for Memorization

• Visual Aids: Drawing a simple picture of the shapes and writing down the lengths can really help.
• Practice: Try solving problems using these formulas. The more you practice, the easier they will be to remember.
• Flashcards: Make flashcards with the formula on one side and an example on the other. This can be a fun way to learn!

These formulas are the building blocks of geometry. Knowing them will give you a strong base as you continue your math journey!