All areas are measured in squares.
Let one side of a square be s.
This is a square s or s2.
Ifs equals 1 inch then this would be 1 square inch.
Ifs equals 1 foot then this would be 1 square foot, etc.
Consider the area of the above. The area of A is one
square s or Sz; of B is s~, etc. The area of the whole is
A+ B+ C+ D = s2+ sz+ s2 + s2 = 4s2. What is the length
of one side? It is obviously 2s, so in the above the area
is 2s x 2s = 4s2.
The area of a square is the product of two of its sides
and since both sides are equal, it may be said to be the
square of its side.
NOTE: The area of any plane surface is the measure
of the number of squares contained in the object. The
unit of measurement is the square of the unit which
measures the sides of the square.
AREA OF A RECTANGLE
Establish a side of the small square as s and write
the formula 3s x 4s = Area. But L = 4s and W = 3s, so
our formula becomes
L x W
area of a rectangle
length of a rectangle
width of a rectangle
AREA OF A CROSS SECTION
The cross section of an object is a plane figure
established by a plane cutting the object at right angles
to its axis. The area of this cross section will be the area
of the plane figure produced by this cut.
The area of the cross section is L x W.
The most common units are square inches, square
feet, square yards and in roofing, squares.
1 square foot
= 144 square inches
1 square yard
= 9 square feet
1 square of roofing = 100 square feet