• The One of These Things Is Not Like the Other activity requires students to isolate the specific characteristics of shapes in a more general way than simply identifying which object is out of place. Since the characteristics of the shapes include color, which is not subject to change by dilation, students must reason from the specific to the general in order to apply the scale factor, dilate, and assess the result.
• Student responses to the exit ticket activity will vary according to their choice of shape, number of sides and vertices, length of sides, and location. Make a qualitative evaluation of the results first: Is the scale factor 3 drawing larger or smaller than the original? Is the scale factor  drawing larger or smaller than the original? Has the student applied the scale factor uniformly in all directions?

“How many of you have seen Sesame Street?” Describe a little bit about the show for students. [IS.5 - All Students] “There is a character named Grover and he sings a song called ‘One of These Things is Not Like the Other.’ I am going to show you some images and you have to tell me which object does not belong and why it does not belong.” Put on the overhead or document camera the One of These Things activity sheet (M-G-5-3_One of These Things.doc). Students have two choices for #1. The blue square doesn’t belong because it is the only one that is not red or the large square doesn’t belong because it is not small. Students also have two choices for #2. The small face doesn’t belong because it is not large or the teary face doesn’t belong because it is not smiling. “Let’s say we do not have the ability to change the color or the face. What could we do so that we go from two objects not belonging to only one object?” Allow students time to think. [IS.6 - All Students] “Well, how can we do that?” Hopefully students say make the large square smaller and make the small face larger.

“Today we are going to learn how to make geometric figures larger or smaller in the coordinate plane. How many of you have been to an eye doctor before?” Allow students to respond. “How many of you have ever had the pupils of your eyes dilated for a medical reason? Does anyone know what it means for the pupils of your eyes to dilate?” [IS.7 - All Students] Let students raise their hands and have a discussion about eye dilation. A similar discussion may include camera lenses that are adjustable to let in more or less light. “In order for the doctor to check your eyes, some drops are put in your eyes that force your pupils (the black part of your eye) to stay open. So when you look at someone who just had his/her eyes dilated, his/her pupils are larger than normal. Today we are going to learn what dilation means in geometry.”

Hand out the Lesson 3 Graphic Organizer (M-G-5-3_Lesson 3 Graphic Organizer.doc and M-G-5-3_Lesson 3 Graphic Organizer KEY.doc) and fill it out with students.

Part 1

Pair up students and give them four sheets of graph paper. [IS.8 - All Students] Each student creates his/her own picture made up of geometric figures. Tell students to keep it simple. For example: a house made up of a large square, a triangle for the roof, a rectangle for the door and four square windows. When students have completed their pictures, they switch pictures with their partner. They then use another sheet of graph paper to dilate the picture by a factor of 3. When they’re done, have the partners check one another’s work. Then they draw another picture and swap again. This time they have to dilate the picture by a factor of  (or ). If there is time, students can do it one more time, but for half the shapes have them dilate by a factor greater than 1 and for the other half they dilate by a factor between 0 and 1. Display student work in the classroom.

Part 2

Hand out the Lesson 3 Exit Ticket (M-G-5-3_Lesson 3 Exit Ticket.doc and M-G-5-3_Lesson 3 Exit Ticket Key.docx) to evaluate whether students understand the dilation concepts. [IS.9 - Struggling Learners and ELL Students]

Extension:

• Create a diagram of your classroom from a bird’s-eye perspective. Direct students to measure objects throughout the room and then have them measure the objects in the diagram. They need to determine the dilation factor of each object. For example, if their desk is 24 inches wide and in the diagram the desk is 1 inch wide, the dilation factor is .
• When students understand a positive dilation factor, ask them what would happen if the dilation factor was a −2 or a . Then they can do the exit ticket, finding the coordinates of the image of their figure after they have applied a factor of −2.