www.justforkidsonly.com


HOME /SITE MAP / NEXT / BACK TO READY REFERENCE


Google


|| READY REFERENCE ||

 

Surface Measurement

 

Perimeter and Area - 2

 

Dear friend,

you must have noticed in the previous section that

by adding more lines or by bending the line

we can cover some area.

 

Thus we added one more dimension.

 

By adding one more dimension we made different shapes or two dimensional figures.

 

Two dimensional geometric figures now have Surface Area.

 

The surface area of any figure (two dimensional or three dimensional) is

the sum of all the areas of all the shapes that cover the surface of the object.

 

Surface area is measured in Square Units.

 

You have to keep in mind that while calculating the surface area you have to use the same units for all the measurements.

For example, you can not use inches for length and centimeters for the width.

 

There are different equations for different geometric figures to find out their surface area.

 

For example:

 

For square you multiply length x 4 = its surface area in square units.

For triangle you multiply length of its base x its height = its surface area in square units.

For Rectangle you multiply its length x its width = its surface area in square units.

For circle the equation is pi x r, where Pi is a constant. Pi = 3.141592... and r is radius of the circle.

 

Perimeter:

The distance around a figure is called its perimeter.

 

This is equal to the sum of its all sides.

 

Now let us see some of the equations for surface areas for some common geometric figures.

                    

 

 surface area = a x a = a, perimeter = a + a + a + a

      = 4 x a

 = 4a

Square    

 

surface area = a x b = ab,

perimeter = a + b + a + b

           = 2a + 2b

           = 2(a + b)

Rectangle

 

 

 

 

surface area = b x h = bh, perimeter = a + b + a + b = 2a + 2b = 2(a + b)
Parallelogram    

 

surface area = h/2 + (b1 + b2), perimeter = a1 + b1 + a2 + b 2
Trapezoid    

 

surface area = pi r x r = pi r, perimeter = pi x 2r

                = pi x d

Circle   where d is diameter of the circle

 

surface area = pi x r1 x r2

                      = pi r1r2,

perimeter there is no simple exact formula
Ellipse   Some formulas are simple but not exact, while some formulas are exact but not simple

 

surface area = 1/2 x (b x h) = 1/2 (bh) perimeter = a + b + c
Triangle    

 

Surface area of a regular polygon = (1/2) x n x sin(360/n) x s,

where n = number of sides,

s = length from center to a corner

 

Table of Surface Measure

 

Traditional System

 

144 square inches = 1 sq. ft.

9 square feet = 1 sq. yard

30 1/4 sq. yds. = 1 sq. rod

160 sq. rods.  = 1 acre

640 acres = 1 sq. mile

1 acre = 208.71 ft. x 208.71 ft.

 

Table of Surface Measure

 

Metric System

 

meter x 10 = decameter

meter x  100 = hectometer

meter x 1000 = kilometer

 

 

Conversion between metric and customary systems

 

CUSTOMARY to METRIC
     
From multiply by To get
     
square feet 0.0929 square meters
square yards 0.8361 square meters
square miles 2.59 square kilometers
     
     
     
METRIC to CUSTOMARY
     
From multiply by To get
     
square kilometers 0.3861 square miles
hectares 2.4710 acres
     
     
     

   

 



HOME /SITE MAP