Lesson
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Modeling/
Multiple Representation 



Perimeter
is the word used to describe
the distance around the outside of an object or shape.
You can use
counting units to
find the perimeter of a shape, by counting the number of sides that
touch the outside of the shape. 
Example 

Find the
perimeter of this square using
counting units.

Count the number of
sides that touch the outside of the square. There are
3 counting units
on each side of the square and there are 4
sides to the square (3 + 3 + 3 + 3 = 12).
The
perimeter
is 12
units. 
Area
is the number of square
units needed to cover a flat surface.
You can use counting units
to find the area of a shape, by counting the number of squares
inside of it.
1 square unit 
Example 

Find the
area of this shape using
counting units. 
Count the number of
squares in the whole shape.
The
area
is
13 square
units because there are 13 squares in the shape. 
Sometimes you need to
count half squares
to find the area
of a figure.
Example 

Find the
area of this shape using
counting units. 
Count the number of
whole squares in the shape first. Then
count the half square.
The
area
is
8
1/2
square units
. 
Volume
is the number of
cubic units needed to fill a space figure.
You can use counting units
to find the volume of a shape, by counting the number of cubes.
1 cubic unit

Example 

Find the
volume of this shape using
counting units. 
Count the number of
cubes in the shape.
The
volume
is
5 cubic units. 

Remember:
You can use
counting units to
measure the
perimeter, area, or
volume of a shape or object. 

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