Transcript Perimeter and Area MiniLesson

This button will take
you back a slide.
Perimeter
Make sure you have your mini-lesson paper
in front of you.
You will know you need to write something
on the notes because it will be underlined.
The Mini-Lessons are meant to be mini! Only do the
assigned part each day.
Today you will only work on the notes and Part A.
Click the forward button to view the next
slide.
Perim eter is the distance around the rim of a figure.
The writing above is underlined. This means there is
something for you to write on your paper.
Read the definition out loud.
I can’t hear you! 
Do you notice anything similar about the word
perimeter and the definition?
Look above!
Now watch me walk around the perimeter
of my garden.
Perim eter is the distance around the rim of a figure.
With your finger, trace
around the perimeter of the
triangle and the hexagon.
The perimeter of a circle is
called the circumference.
Trace your finger around
the circumference of the
circle.
Perim eter is the distance around the rim of a figure.
Let’s say my garden
has a length of 5 feet
and a width of 3 feet.
As I walk along the perimeter of
my garden I walk a length of 5
feet, then a width of 3 feet, then
another length of 5 feet, and
then another width of 3 feet.
5 ft
3 ft
To find the perimeter of my garden
I just have to add all the sides.
5ft + 3ft + 5ft + 3ft = 16 ft
To find the perimeter of a polygon
(many sided figure), you add all
the sides.
How would you find the
perimeter of a triangle?
4 cm
3 cm
Add all the sides!
4cm + 3cm + 8cm = 15 cm
8 cm
Perim eter is the distance around the rim of a figure.
However, now that you are in pre-algebra, you need to get
into the habit of using formulas. Rectangles have a
special formula for you to use to find the perimeter.
5 ft
3 ft
To find the perimeter of a
rectangular figure use:
P = 2l + 2w
“Perimeter equals two times
the length (l) plus two times
the width (w).”
The perimeter of my garden can be found by “plugging-in”
the length and width:
P = 2l + 2w
P = 2(5) + 2(3)
P = 10 + 6
P= 16 ft.
Perim eter is the distance around the rim of a figure.
Now we are going to find the perimeter of my circular
pool. The perimeter of a circle is called the
circumference.
Before I tell you how to find circumference, let
me go over a little vocabulary.
r
The distance from the center of a circle to
the outside is called the radius.
Last thing is Pi. Pi is represented with the symbol 
 = 3.14159…(goes on forever! It is irrational.)
Pi represents the number of times the diameter of a circle fits
around the circumference of the circle.
Perim eter is the distance around the rim of a figure.
Remember, the perimeter of a circle is called the
circumference.
6 ft
To find the circumference of a circle, use
C = 2r
That is “circumference equals two times Pi
times radius.”
If the radius of my pool is 6 feet, then I can find the
circumference of the pool by “plugging into” the formula.
(You can use 3.14 for Pi)
C = 2r
C = 2 x 3.14 x 6 ft
C = 37.68 ft
The distance around my pool is 37.68 feet.
OK it is time to work on Part A.
Remember to attempt to solve the problem first
before you watch the solution on the following
slide.
Show all of your work!
No calculators.
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
1.) Find the perimeter of the rectangle.
5 ft
7 ft
Try solving the
problem before
moving to the
next slide.
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
1.) Find the perimeter of the rectangle.
5 ft
Your math should
look something
like this…
7 ft
To find the perimeter, use P = 2l + 2w
P = 2(7) + 2(5)
P = 14 + 10
P = 24 ft
Did you get 24 feet?
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
2.) Find the perimeter of the triangle
(all sides are equal):
3 cm
Try solving the
problem before
moving to the
next slide.
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
2.) Find the perimeter of the triangle
(all sides are equal):
Your math should
look something
like this…
3 cm
To find the perimeter, add all the sides.
There are three sides of 3 cm.
3 cm + 3 cm + 3 cm =
Did you get 9 centimeters?
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
3.) Find the circumference of the
circle:
5 cm
Try solving the
problem before
moving to the
next slide.
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
3.) Find the circumference of the
circle:
5 cm
Your math should
look something
like this…
To find the circumference use:
C = 2r
2 x 3.14 x 5 cm =
Did you get 31.4 centimeters?
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
4.) Find the perimeter of a rectangle
with a length of 6 yards and a width of
8 yards.
Try solving the
problem before
moving to the
next slide.
Make sure your answer includes the units (feet, inches, centimeters, etc.)!
Perim eter is the distance around the rim of a figure.
*To find the perimeter of a polygon (many sided figure), you add all the sides.
*To find the perimeter of a rectangular figure, use P = 2l + 2w
*To find the circumference of a circle, use C = 2r
4.) Find the perimeter of a rectangle
with a length of 6 yards and a width of
8 yards.
Your math should
look something
like this…
I find drawing a picture with labels makes problems like this easier.
6 yd
To find the perimeter of a rectangular figure, use P = 2l + 2w
P = 2(6) + 2(8)
P = 12 + 16
P = 28 yds
8 yd
Did you get 28 yards?
Make sure your answer includes the units (feet, inches, centimeters, etc.)!