Objective:
Approximation and Precision
In this lesson you will demonstrate your understanding
of how precision is affected by the unit of measurement.
You will need to know when estimating is appropriate
and how to estimate to obtain reasonable approximations.
If you need to check a word's definition, please go to the glossary by clicking the Vocabulary button
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Attribute
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Area
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Perimeter
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Volume
- Approximation
- Accurate
- Polygon
| When you are asked to estimate, be sure to solve
the problem by estimating, not by computing the answer
and then rounding. Work the entire problem by estimating
without any actual computing of the solution. You
may not receive full credit for your answer if you
compute first and then estimate that answer. |
| As you work with measurement, always be sure to
determine what units are in your answer and then
label your answer such. For example, don't say that
the area of the rectangle is 20. You want to be sure
to include the units of measure as well. So the area
of the rectangle would be 20 squared feet. Remember
if you are finding area, the units are squared and
if you are finding volume, the units are cubed. |
| To find the perimeter of a polygon or geometric
figure, you find the distance around it. You will
add the lengths of all sides to arrive at the perimeter.
When you find perimeter, you are working with only
one dimension as you measure around the figure. Since
you are only measuring and adding the lengths around
the figure, the units are labeled as one dimension,
usually just cm, ft, yd, mi, or others. The units
are NOT squared or cubed when finding perimeter
because you are working with one dimension. |
To find the area of a rectangle, use the formula,
L x W, where L is the length of the rectangle and
W is the width of the rectangle. When finding the
area of a rectangle, your results will be in the
units of measurement squared. The reason the units
are labeled squared is because you are working with
only two dimensions when working with area, length
and width. This is often represented as the
units of measure squared or to the second power.
For example, 15 cm2 or
it may be written as 15 squared cm. A = lw
Find the area of a rectangle 20
feet long and 12 feet wide.
A = l x w
A = 20 x 12
A = 240 feet squared
|
To find the area of a triangle, you
use the formula, 1/2 x b x h, where b represents
the base of the triangle and where h represents the
height of the triangle. When finding the area of
a triangle, your results will be in the units of
measurement squared. The reason the units are labeled
squared is because you are working with only two
dimensions when working with area, length and width. A
= 1/2 bh
For example:
Find the area of a triangle with
a base of 10.2 feet and a height of 3.5 feet.
A = 1/2 bh
A = 1/2 (10.2)(3.5)
A = 35.7/2
A = 17.85 feet squared
|
Volume of a Rectangle
One way to find the volume of a rectangle is
to multiply the dimensions, the length, the width,
and the height of the rectangle. Since we find
volume of a rectangle using three dimensions,
length, width, and height, the answer will be
in units cubed. This is often represented as
the units of measure cubed or to the third power.
For example, 12 cm3 or
it may be written as 12 cubic cm. You use the
following formula: V = lwh
For example:
Find the volume of a rectangle
with the dimensions of 13.5 cm in height, 21
cm long, and a width of 6.2 cm.
V = lwh
V = 21 x 6.2 x 13.5
V = 130.2 x 13.5
V = 1757.7 cm cubed
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Example
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