Ms. CuervoCAHSEE Prep

AREA

Area

7MG 2.1 Students will find the area of rectangles, squares, trapezoids, parallelograms, triangles and circles.

Vocabulary:

Area – The number of square units needed to cover a region

Length- The longer side

Width- The shorter side

Base – The side of a two-dimensional figure to which the height is drawn

Height- The perpendicular distance from the vertex to the base of a triangle, or the perpendicular distance between the two bases of a trapezoid

Squares• Squares have equal sides• You must multiply base with height (these are the equal sides of the square) to find the area of a square

A = bh5 feet

A = b x h

A = 5 ft x 5 ft

A = 25 ft2

Rectangles

• You must multiply base with height (same thing as length and width) to find the area of a rectangle

A = bh

12 yards

6 y

ard

s A = b x h

A = 12 yards x 6 yards

A = 72 yards2

How do you find the area of a rectangle? Click here to watch VIDEO!

Triangles• You must multiply base x height and divide by 2 to find the area of a triangle (the areas of the two triangles together equal the area of the rectangle)

• The height is the vertical distance from the vertex to the base • Be careful not to confuse the height with one of the sides of the triangle

base

height

A = ½ (base x height)

5.5 in

7 inches

A = ½ bh

A = ½ (7in)(5.5 in)

A = ½ (38.5in2)

A = 19.25 in2

How do you find the area of a triangle? Click to watch VIDEO!

Parallelograms• The height of the parallelogram is not the same as the side length of the parallelogram• Sometimes you will be given 3 dimensions for a parallelogram: the base, the height, and the slanted side’s length• The only two dimensions you need to calculate area are the base and the height

A = bh

7 ft

4 ft 5 ft

A = bh

A = 7 ft x 4 ft

A = 28 ft2

How do you find the area of a parallelogram? Click here to watch VIDEO!

Trapezoids• The formula for the area of a trapezoid is just like the formula for the other quadrilaterals you know (rectangles, squares, and parallelograms) except that you must use the average base length• You must use the average base length because the lengths of the bases are not the same (base 1 and base 2)

A = (b1 + b2) h

24 feet

6 feet

5 feet

A = (b1 + b2) h 2

A = (4 ft + 6ft) 5ft 2

A = (10 ft) 5ft 2

A = (5 ft) 5ft

A = 25 ft2

How do you find the area of a trapezoid? Click here to watch VIDEO!

Circles

A = r2

A = r2

A = (3.14)

(3in2)

A = (3.14)

(9in2)

A = 28.26in2

6 in

How do you find the area of a circle if you know the diameter? VIDEO!

How do you find the area of a circle if you know the radius? VIDEO!

A = r2

A = (3.14)

(4in2)

A = (3.14)

(16in2)

A = 50. 24 in2

4 in