1. How it Affects Perimeter and Area
Changing Dimensions
How it Affects Perimeter and Area

2. Changing Dimensions Directions
As you go thru this Power Point Presentation, you will be asked to make some predictions and do some calculations. Show all of your thinking on your page, and use your grid paper for your drawings.
This rooster on the slide means that you will be asked to do something.
So pay attention!!

3. Guessing Time
Take the original shape and guess what it would look like if the dimensions were doubled (meaning x2)
Original A B C

4. Guessing Time
Take the original shape and guess what it would look like if the dimensions were doubled (meaning x2)
Original B

5. Try #2
Guessing Time
Take the original shape and guess what it would look like if the dimensions were doubled (meaning x2)
Original A B C

6. Try #2
Guessing Time
Take the original shape and guess what it would look like if the dimensions were doubled (meaning x2)
Original C

7. The Real Change When you change Dimensions
Notice: The fingers are pulling the shape both wider and taller. Left/Right and Up/Down are changing.
Length & Width

8. Time for you to change Shapes that is...
On your grid paper, make the original shape and then draw a new shape with dimensions that are triple (x3) the original.

9. Ready to see if you got it right?

10. Well, Did You?
3 across
Original
3 down
Triple Size

11. Find a Rule What does it mean to change the dimensions of an object?
It means to change length and width the same way.
They both get multiplied by the same thing

12. How Does Perimeter Change?
Draw the shape on your grid paper
Find the perimeter

13. How Does Perimeter Change?
Draw the shape on your grid paper
Find the perimeter
Perimeter is 8 units 1
= 8 1 3 3

14. How Does Perimeter Change?
Now draw a second figure with dimensions twice as big as the first
Find the perimeter

15. How Does Perimeter Change?
Now draw a second figure with dimensions twice as big as the first
Find the perimeter 6 2

16. How Does Perimeter Change?
Time for Lots of practice....
Draw the shapes and find the perimeters.

17. How Does Perimeter Change?
Time for Lots of practice....
Halve this one and find the perimeter
Triple this one
And find the perimeter
These won’t be done up here for you.

18. How Does Perimeter Change?
Final Analysis...
Original Perimeter
Dimension Change
New Perimeter
8 in
12 in
28 in
X 2
X 3
X 1/2
16 in
36 in
14 in
Do you see the rule?

19. How Does Perimeter Change?
Final Analysis...
Original Perimeter
Dimension Change
New Perimeter
8 in
12 in
28 in
X 2
X 3
X 1/2
16 in
36 in
14 in
Perimeter will change exactly as the dimensions change.

20. All area question are answered in
What Does Area Measure?
Area measures how many squares are in an shape.
A square
has two
dimensions
30 square units in this shape
All area question are answered in
units squared or units2

21. Does Area Change? Let’s unfold a rectangle and see (doubling the dimensions)
Starts as a 4 x 3 rectangle
12 sq. cm

22. Does Area Change? Let’s unfold a rectangle and see
Make it Twice as tall
12 24 sq. cm

23. Does Area Change? Let’s unfold a rectangle and see
Now make it twice as wide
sq. cm

24. Does Area Change? What happened there?
I doubled the size of a rectangle
I made it twice as tall and twice as wide
sq. cm
I thought the area would double just like perimeter did – but it didn’t
The AREA doubled and doubled again.

25. Paper Foldy Thing Look at the folded, colored rectangle
When you unfold it (x2 size), you unfold it twice.
What happened to the area?
Repeat after me... You multiply the area and multiply the area again.

26. Does Area Change? Drawing and Math Time
Draw the shapes as they are
Find the area of each
Redraw them following the dimension changes given 3 5 8 2 3 12
Area=
Area=
Area=

27. Does Area Change? Draw and Math Time
Redraw them following the dimension changes given 3 5 8 2 3 12
Area= 6 sq. in.
Area= 15 sq. in.
Area= 96 sq. in.
Dimensions x 4
Dimensions x 3
Dimensions x 1/4

28. Does Area Change? Draw and Math Time3 2
Area= 6 sq. in.
And It Became: 12
Dimensions x 4 8
New Area: ?

29. Does Area Change? Draw and Math Time5 3
Area= 15 sq. in.
Dimensions x 3
And It Became: 15
New Area: ? 9

30. Does Area Change? Draw and Math Time8
And It Became:
How much Room
Do We Need? 2 12 3
Dimensions x 1/4
New Area: ?

31. Does Area Change? Draw and Math Time8
And It Became 2 3 12
New Area: ?
Dimensions x 1/4

32. How Does Area Change? Final Analysis... 6 in2 15 in2 96 in2 X 4 X 3
Original Area
Dimension Change
Work Area
New Area
L W
6 in2
15 in2
96 in2
X 4
X 3
X ¼
6 x 4 x 4
15 x 3 x 3
96 X ¼ x ¼
96 in2
135 in2
6 in2
Do You See a Simple Rule?

33. Since area is measured in SQUARE units. It changes twice. (L and W)
How Does Area Change?
Final Analysis...
Original Area
Dimension Change
Work Area
New Area
L W
6 in2
15 in2
96 in2
X 4
X 3
X ¼
6 x 4 x 4
15 x 3 x 3
96 X ¼ x ¼
96 in2
135 in2
6 in2
Since area is measured in SQUARE units. It changes twice. (L and W)

34. Changing Area works for all Shapes
Final Thought
Changing Area works for all Shapes
A=12.5 in2
Dimension
Change x2
12.5 x 2 x 2 = 50 in2
A=8 in2
Dimension
Change x3
8 x 3 x 3 = 72 in2

35. Pay attention to your Teacher
What Are You Looking At!
The Show is Over
Pay attention to your Teacher
Slackers!