Dilations & Measurement Lesson, TEKS 8.10D

​Do your Warm-Up!

What is our TEKS?

TEKS 8.10D:

The student will model the effect on linear and area measurements of dilated two‐dimensional shapes.

Dilations & Measurement, TEKS 8.10D(S)

It's time for our lesson . . .

​Dilations & Measurement

You can take notes in your journal or lined paper, but be sure to pay attention to the video.

Open Ended

What is one thing that you learned from the video?

Dilations and Perimeter:

• The new perimeter is equal to the old perimeter multiplied by the scale factor, k.

• P' = kP

Dilations and Area:

• The new area is equal to the old area multiplied by the scale factor squared, k².

• A' = k²A

Poll

Self-Assessment:

• I'm an expert. I got this! (I can teach this skill to others.)

• I'm a Practitioner. I can do this with more practice. (I can use the practice page and answer key on the Unit Checklist to improve my skills.)

• I'm a Novice. I need help learning this skill! (I can come to tutoring to get the help I need, or I can ask an Expert for help.)

Multiple Choice

What is the formula that compares the perimeter of the image with the perimeter of the pre-image?

• $$P'=P\cdot k$$

• $$P=P'\cdot k$$

• $$P=2l+2w$$

• $$P'=P\cdot k^{2\ }$$

Multiple Choice

What is the formula that compares the areas of the image and pre-image?

• $$A'=\ A\cdot k$$

• $$A=A'\cdot k$$

• $$A'=A\cdot k^2$$

• $$A=bh$$

Pay attention as you work through the problems with the teacher.

Time for Guided Practice . . .

Dilations & Measurement, TEKS 8.10D(S)

Multiple Choice

I DO:

If a rectangle has an area of 48 cm², what would be the area of a similar rectangle if the dimensions are doubled?

• 96 cm²

• 192 cm²

Multiple Choice

WE DO:

Figure ABCD is then dilated using a scale factor of 4. What is the perimeter of the new figure?

• 32

• 64

Multiple Choice

YOU DO:

Suppose the dimensions of a pentagon with an area of 12 in² are tripled. What would the area of the new pentagon be?

• 108 in²

• 36 in²

​​Use your journal, lined paper, or dry erase board to practice solving the Quizizz problems on your own. Do as many problems as you can until the timer rings.

Time for Independent Practice . . .

Dilations & Measurement, TEKS 8.10D(S)

Multiple Choice

If a shape is dilated by a scale factor of one-half, what is the resulting perimeter? 

• The same as the perimeter of the pre-image

• The new perimeter is bigger than the pre-image

• The new perimeter is smaller than the pre-image

• The new perimeter is 4 times the original

Multiple Choice

A shape is dilated. To find the area of the figure you would...

• Multiply the area of the pre-image by the scale factor.

• Multiply the area of the pre-image by the scale factor squared.

Multiple Choice

If a shape is dilated by a scale factor of 1/2, what is the resulting perimeter?

• The new perimeter is 1/2 the original

• The new perimeter is 1/4 the original

Multiple Choice

Triangle ABC is dilated by a scale factor of 5. To find the perimeter of the image after the dilation, you would multiply the perimeter of the pre-image by...

• 5

• $$5^2$$

Multiple Choice

A quadrilateral is dilated by a scale factor of 3.5. Which statement is true about the figure.

• The figure's perimeter is 12.25 times the perimeter of the pre-image.

• The figure's perimeter is 7 times the perimeter of the pre-image.

• The figure's area is 12.25 times the area of the pre-image.

• The figure's area is 7 times the area of the pre-image.

Multiple Choice

A shape is dilated. To find the perimeter of the image you would...

• Multiply the perimeter of the pre-image by the scale factor.

• Multiply the perimeter of the pre-image by the scale factor squared.

Multiple Choice

A shape is dilated by a scale factor of $$\frac{1}{2}$$  . The peremeter of the image is...

• $$\frac{1}{2}$$  the perimeter of the pre-image. 

• $$\frac{1}{4}$$  the perimeter of the pre-image. 

Multiple Choice

A shape is dilated by a scale factor of $$0.75$$  . The area of the image is...

• .75 times the area of the pre-image. 

• .5625 times the area of the pre-image. 

Time for your Mastery Check:

It's time to assess your skills using a STAAR-related problem. Carefully select your answer to the next problem to test your knowledge. You will use this for your Self-Assessment.

Dilations & Measurement, TEKS 8.10D(S)

Multiple Choice

A figure is dilated by a scale factor of 4. Which of the following statements about the figure must be true?

• The perimeter and area are both multiplied by 4.

• The perimeter is multiplied by 4 and the area is multiplied by 16.

• The perimeter and area are both divided by 4.

• The perimeter is multiplied by 16 and the area is multiplied by 4.

Poll

Self-Assessment:

• I'm an expert. I got this! (I can teach this skill to others.)

• I'm a Practitioner. I can do this with more practice. (I can re-do this lesson through Google Classroom.)

• I'm a Novice. I need help learning this skill! (I can come to tutoring to get the help I need, or I can ask an Expert for help.)

Video: Dilations & Measurement

Are you a Novice and need extra support? If so, watch Mrs. Wilson's teaching videos of the lesson and practice problems.

Blank Notes: Dilations & Measurement