Do you remember the definition of a rectangle? A rectangle has four
sides and opposite sides are parallel plus the each of the four corners
is 90 degrees or perpendicular. That's a complicated definition for
a shape that you see all the time. Why, the computer monitor screen
that you are looking at right now is probably an example of a rectangle.
A square is a specialized rectangle where all the sides are equal.
What do you know about the geometry of a rectangle? To calculate
the perimeter of a rectangle, the distance around the outside, you
simply add out the length of the four sides. An even easier formula
Perimeter of a rectangle = 2 x length + 2 x width
The area of a rectangle is also easy to calculate.
Area of a rectangle = length x width
Rectangles and squares are found everywhere around you. Make a list
of all the things around you at this moment that are rectangular or
square. A possible list includes paper, Post-it notes, calendar, books,
windows, walls, ceiling, floor, the top of the desk, sides of the
desk, desk drawers, waste basket and calculator. What else do you
see that is rectangular or square?
If you have a tile floor, you may see square tiles or rectangular
tiles. If you have a wooden floor, each board is a long and narrow
rectangle but it's still a rectangle. Maybe you have carpet that covers
the entire floor. The room you are in is most likely a rectangle or
square. Think about how easy it is to figure out how much flooring
you need to buy.
Room is 10 feet by 12 feet
Area to cover is 10 feet x 12 feet = 120 square
If you want to buy floor tile and each tile is a 12 inch
square, how many tiles do you need for the room? Each tile is 1 square
foot, so you need 120 tiles.
Wooden flooring is a little more complicated because boards can be
3 inches wide and 8 feet long. Each board would cover 1/4 foot x 8 feet
or 2 square feet. So you would need 60 boards.
Carpet can be just as easy or a little harder depending on the size
of the room. Carpet comes in rolls that are either 12 feet or 14 feet
wide. This time it's easy - just measure 10 feet of carpet off of
Rectangles and squares are just easy to work with. Imagine if your
room was circular and you wanted to put in new flooring. Remember
that the area of a circle is calculated as
Area of a circle =
number 3.14 and r2 is the radius times itself. But the radius is measured
from the center point of the circle to the outside of the circle or
the radius is half the diameter, the distance across the circle again
at the center point.
Do you have a headache already from trying to put new flooring into
a circular room? The geometry of a rectangle or square is so easy
to work with that land measurements like house lots, building measurements
and lots of other useful everyday objects are rectangular or square.
Another reason that so many buildings are rectangular is that straight
walls and floors have built-in strength. We say that they are structurally
sound because it's easy to put in studs, upright boards inside the
walls, to support the structure. Your house or school probably has
studs every two feet inside the walls.
Do you now have some idea why it is important that someone on this
planet understands the geometry of a rectangle?