# Area Area problems involve finding the surface area for a two-dimensional figure.

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Area Area problems involve finding the surface area for a two-dimensional figure.

Area Area problems involve finding the surface area for two-dimensional figures. What is surface area: it is the amount of space on the front of a two-dimensional figure. Suppose you were painting a wall, you would need to know the surface area so you would know how much paint to buy.

Two-Dimensional Two dimensional means a shape has only two measurements: either length and width, base and height, etc. Example: the Area formula for a rectangle is: A = lw or Area = length times width You used two dimensions to calculate with. What dimension you don’t calculate is depth.

What Shapes? We will be calculating area for: Squares Rectangles
Rhombus Parallelogram Trapezoid Triangle Circle

Square The area formula for a square is: s²
That is side squared. Remember all sides of a square are equal Example: the area for a square with sides of 5 inches: A = 5² or 25 inches²

Rectangle The area formula for a rectangle is: A = lw
That means A = length times width Example: a rectangle with a length of 20 feet and a width of 10 feet: A = 20 • 10 or 200 ft.²

Rhombus & Parallelogram
They have the same area formula: A = bh or Area = base times the height The base and height will be marked so you can calculate very easily. Example: a parallelogram with a base of 10 cm and a height of 4 cm = A = 4 • 10 = 40cm²

Trapezoid The area formula for a trapezoid is the most difficult: ½h(b₁ + b₂) That is half (.5) the height times the sum of the top base and the bottom base.

Circle Area formula for a circle: A = πr² Remember: pi = 3.14 (π)
r = radius² Example: circle with a radius of 3 inches: 3.14 • 3² = 3.14 • 9 or in.²

Triangle Area formula for a triangle: A = ½bh or
Area = one half (.5) the base times the height Example: a triangle with a base of 12 mm and a height of 10 mm = .5 • 12 • 10 = 60mm²

Area Is it a useful problem especially if you are:
In the field of construction In the field of roofing In the field of plastering or painting In the field of sewing, designing

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