Calculating Area

Calculating the area of simple geometric shapes is one of the activities you will do in your math class. Area is basically the size of a shape. For basic shapes like rectangles you just multiply the width with the length to get the area. Finding the area of a circle is however a little different from the other shapes. The formulae for calculating the area of a circle is ?r2. Where ? (Pi) is the ratio of the circumference to the diameter of the circle. The Pi is a constant whose value is calculated to be equal to 3.1416 when calculated to four decimal places. The 'r' in the formulae represents the radius of the circle. The radius is the fixed distance from the center of the circle to its boundary. The radius is half the diameter which is the longest straight line that passes through the center of the circle to its boundaries. You can use either the radius or the diameter to calculate the area of a circle. Here is an example, solve for the area of a circle with a radius of 7 centimeters. We use the formulae; area = Pi x radius squared. Since we already know the Pi which is a constant and the radius we need to just substitute the formulae with the figures, thus, A = ?r2. Area = 3.1416 x 72 = 3.1416 x 7 CM x7 CM = 153.94 CM2, rounded off to two decimal points. You can also use an area of a circle calculator at this link.

If for the same circle you have the diameter and not the radius, you can still find the area using the diameter. Area = Pi x Diameter squared, divided by four. A = (3.1416 x 142) ? 4. = 615.7536 ? 4 = 153.94CM2.

For other shapes that have more than two dimension we can also calculate the surface area. Surface is the total area occupied by the surface of the object. For example, we can calculate the surface area of a pyramid by adding the area of its base to the area of the lateral faces. Hence SA = BA + LA. The base of a pyramid can be in the shape of any polygon but the lateral faces are always triangles. Therefore in calculating the area of the base you use the area formulae for the respective polygon. If it is a rectangle just multiply the width and the length. The area of formulae for the area of a triangle is 1/2 bh where h is the height of the triangle and not the pyramid. Therefore surface area of a rectangular based pyramid is (L x W) + ( 1/2 B x H). the surface area answer is in square units. Learn more about multiplying fractions here.