Lesson 7 of 8
Perimeter and Area
Perimeter is the distance around the edge of a flat shape. Area is the space inside it, measured in square units. Keep these formulas in your pocket.
FORMULA
Rectangle: perimeter = 2 times length + 2 times width. Area = length times width.
FORMULA
Triangle area = one half times base times height. Parallelogram area = base times height.
FORMULA
Trapezoid area = one half times (base1 + base2) times height. Circle area = pi r^2.
Worked example
A triangle with base 10 and height 6 has area = one half times 10 times 6 = 30 square units. A rectangle 8 by 3 has perimeter = 2 times 8 + 2 times 3 = 22 and area = 8 times 3 = 24 square units.
Tip: perimeter is measured in regular units (feet), area is measured in square units (square feet). Watch your units on the test.