Finding AreaPart 1: Rectangles

Math 6

Objectives:

1. Find the area of right triangles, other triangles, special quadrilaterals, and polygons by composing into rectangles or decomposing into triangles and other shapes.

6.G.1

Keys to Geometry

Master the vocabulary1. Polygon

2. Parallel

3. Perimeter

4. Perpendicular

5. Area

6. Rectangle

7. Right angle

8. Line segments

Online Math Dictionaries

http://www.mathsisfun.com/definitions/letter-a.html

http://www.icoachmath.com/math_dictionary/mathdictionarymain.html#P

http://my.hrw.com/math06_07/nsmedia/tools/glossary/msm/glossary.html

What is area? The size of a surface.

The amount of space inside the boundary of a plane (2-dimensional) figure such as a triangle or circle.

How is area found?

There are different methods for finding area depending on what type of polygon you are working with…

This lesson will cover area of rectangles

Rectangle• A 4-sided plane figure • whose sides are formed by line

segments• With all right angles (90°).• Opposite sides are parallel and of

equal length.

Example: A square is a special type of rectangle.

Area of a rectangle (or square)

Use the dimensions of the figure that are known.

Multiply the length by the width.

Find the area of the rectangle below:

Why is the answer expressed as “square units.”

• Area is the outcome of multiplication of two lengths. 7cm x 14cm.

• So cm multiplied by cm = cm².

• The answer must indicate “squared” either by use of an exponent ‘2’ or the word squared or abbreviation ‘sq’.

How is area different from perimeter?

Area is the amount of surface that a figure covers. (INSIDE)

Perimeter is the distance around the outside of a figure. (OUTSIDE)

Since perimeter is a linear measure, not a spatial one, the answer is not in “square units.”

Guided Practice

Find the area of the rectangle below:

Guided Practice

Find the area of a rectangle whose dimensions are:

Length: 12 feet

Width: 15 feet

Guided Practice

A gardener digs a flower bed that is 8 meters long and half a meter wide. What is the area of the flower bed?

Guided Practice

A rectangle is twice as long as it is wide. Its width is 5½ cm. Find the area of the rectangle.

Guided Practice

The label on a tin of paint states that it contains enough paint to cover 10m². I need to paint a wall that measures 2 meters by 4½ meters. Will I have enough paint?

Conclusion

To find the area of a rectangle, we use the most basic formula:

Area = length times width.

A=L x W

This is the starting point for finding area of many other figures.

Assignments

http://mrnussbaum.com/grade5standards/575-2/