Perimeters And Areas

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Perimeters of Triangles and Quadrilaterals

Find the perimeters of triangles and quadrilaterals

Perimeter – is defined as the total length of a closed shape. It is obtained by adding the lengths of the sides inclosing the shape. Perimeter can be measured in ?? , ?? ,?? ,?,?? e. t. c

Examples

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Example 1

Find the perimeters of the following shapes

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Solution

Perimeter = 7? + 7? + 3? + 3? = 20 ?
Perimeter = 2? + 4? + 5? = 11 ?
Perimeter = 3?? + 6?? + 4?? + 5?? + 5 ?? + 4?? = 27 ??

Circumference of a Circle

The Value of Pi ( Π)

Estimate the value of Pi ( Π)

The number π is a mathematical constant, the ratio of a circle’s circumference to its diameter, commonly approximated as3.14159. It has been represented by the Greek letter “π” since the mid 18th century, though it is also sometimes spelled out as “pi” (/paɪ/).

The perimeter of a circle is the length of its circumference ?. ? ????????? = ?????????????. Experiments show that the ratio of the circumference to the diameter is the same for all circles

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The Circumference of a Circle

Calculate the circumference of a circle

Example 2

Find the circumferences of the circles with the following measurements. Take ? = 3.14

diameter 9 ??
radius 3½?
diameter 4.5 ??
radius 8 ??

Solution

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Example 3

The circumference of a car wheel is 150 ??. What is the radius of the wheel?

Solution

Given circumference, ? = 150 ??

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∴ The radius of the wheel is 23.89 ??

Areas of Rectangles and Triangles

The Area of a Rectangle

Calculate the area of a rectangle

Area – can be defined as the total surface covered by a shape. The shape can be rectangle, square, trapezium e. t. c. Area is measured in mm!, cm!,dm!,m! e. t. c

Consider a rectangle of length ? and width ?