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

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!!

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

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

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

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

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

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.

Ready to see if you got it right?

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

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

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

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

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

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

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

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.

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?

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.

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

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

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

Does Area Change? Let’s unfold a rectangle and see Now make it twice as wide 12 24 48 sq. cm

Does Area Change? What happened there? I doubled the size of a rectangle I made it twice as tall and twice as wide 12 24 48 sq. cm I thought the area would double just like perimeter did – but it didn’t The AREA doubled and doubled again.

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.

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=

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

Does Area Change? Draw and Math Time 3 2 Area= 6 sq. in. And It Became: 12 Dimensions x 4 8 New Area: ?

Does Area Change? Draw and Math Time 5 3 Area= 15 sq. in. Dimensions x 3 And It Became: 15 New Area: ? 9

Does Area Change? Draw and Math Time 8 And It Became: How much Room Do We Need? 2 12 3 Dimensions x 1/4 New Area: ?

Does Area Change? Draw and Math Time 8 And It Became 2 3 12 New Area: ? Dimensions x 1/4

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?

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)

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

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