let's take a geometry walk

Let's Take a Geometry WalkAuthor(s): Glenn Nelson and Larry P. LeutzingerSource: The Arithmetic Teacher, Vol. 27, No. 3 (November 1979), pp. 2-4Published by: National Council of Teachers of MathematicsStable URL: http://www.jstor.org/stable/41189485 .

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Lett Do It

LcťsTaHca Georpetry WalH

By Glenn Nelson

University of Northern Iowa Cedar Falls, Iowa and Larry P. Leutzinger Area Education Agency 7 Cedar Falls, Iowa

Showing the relevance of a topic in mathematics to life can make the topic more meaningful to students. Noting the topic's existence and use in the world around us can provide motiva- tion for the study of the topic and op- portunities for real life applications. The study of geometry is a good example. Enterprising teachers have al- ways used objects in the classroom to illustrate geometric terms and ideas. This approach can be extended by tak- ing a geometry walk outside the classroom.

To promote a greater awareness of geometry in the real world, encourage students to note that (1) an object's function or use may determine its shape, (2) aesthetics or appearance

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may determine its shape, and (3) the vocabulary of geometry may be helpful in describing shapes and spatial relationships. A projector screen, for instance, is rectangular because the im- ages displayed on it are generally rectangular and a rectangular screen is easier to roll up than a circular screen would be. An abstract painting or sculpture may use a shape, or combi- nation of shapes, because a particular shape is pleasing in appearance. Many things, such as buildings or furniture, may be shaped as they are because of both function and aesthetics.

As you plan to explore your school building, schoolyard, and nearby neighborhood, make a note of questions that will direct students' attention

to the large role that geometry plays in their lives. Questions should focus not only on shape recognition and use of geometric vocabulary but also on how function and aesthetics determine shape. Sketch a map for your planned walk and mark on it the places where, on your walk, you will ask certain questions. Plan your schedule so that some class time will be available after the walk for a discussion of the students' observations.

Following are samples of questions that you might ask students (and some possible responses). You will be able to think of other questions that are more appropriate for your circumstances and surroundings. Although divergent, meaningful responses to questions

Arithmetic Teacher



about function and aesthetics can be made by youngsters of widely differing ages and abilities. The "correctness" of learners' answers to questions on vocabulary may be dependent on the amount of geometry they have studied in school. You will need to plan your questions accordingly.

Functional Shape 1 . Why is each opening in the bicycle

rack a long, narrow rectangle (fig. 1)? "To keep the wheel and bicycle from falling over." "So the wheel will fit right in." "If it was a circle, you couldn't fit as many bicycles in the rack."

2. Why is a bicycle wheel shaped like a circle instead of a square? "So it's easier to pedal." "It makes the ride a lot smoother." Pretend that you are riding a bicycle with square wheels. Show me how you would look.

3. Why is each end of the frame of the swing set shaped like a triangle (fig. 2)? "Because it makes it steady, so you won't tip it over." If we made the base of each end of the frame shorter, would it be as steady? "No, when you swing way out you could tip it over."

4. Why is a football not round like other balls? "It would be harder to pass, harder to grip." "This way it's easier to cradle it in your arm and carry it without fumbling."

5. Look at that factory's smokestack. Why is it cylindrical? "Because you get a bigger smoke hole with fewer bricks."

Aesthetic Shape 1 . Notice the differences between the

shapes found in that older building and the shapes found in that newer building. In which building would you prefer to work? "The older one. I like all those perpendicular line segments; it looks more solid." Which building would you prefer to draw? "The newer one, 'cause all those triangles make it more interesting."

2. Do you like the shape of that car parked over there? "No, it's too boxy- looking." How would you redesign its shape to look better? "I'd make it lower in front and kind of slope it back more to make it look faster."

November 1979

Fig. 1

Fig. 2

3. Many of the office signs we can see are rectangular, but this one is elliptical or oval- shaped. Why do you suppose Dr. Jones chose this shape for his sign? "It looks nice and it's different. Maybe it's to take your mind off your pain."

4. What do you see in that cloud for- mation? What does it look like to you (fig. 3)? "The state of Texas." "My Aunt Barbara."

5. Look at those two trees, the hemlock and the ash. Which shape do you like better (fig. 4)? "The hemlock, 'cause its boughs are bent toward the ground." "I like the way the big branches of the ash reach toward the sky."

Geometric Vocabulary 1. What kind of angle is formed here

by this guy wire and this telephone pole? "Acute."

2. Which of the letters in our school's name, here on the wall, have line symmetry (fig. 5)? "H, U, M, B, E, T, C, O." Which have a horizontal line of symmetry? "H, B, E, O." Which have a vertical line of symmetry? "H, U, M, T, O." Which have both a vertical line of symmetry and a horizontal line of symmetry? "H, O."

3. Which of the letters in the school name would be examples of closed curves? "O AND B."

4. From here I see a large sign, shaped like a regular octagon. What

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color is it and where is it? "It's red and it's the stop sign at the corner."

5. What shape is that yield sign (fig. 6)? "A triangle."

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After the Walk Back in the classroom, list and discuss the instances of geometry that the class saw. Follow-up activities provide a challenge to all students and give your more creative thinkers an opportunity to extend themselves. The following are examples of follow-up activités that might be used with a class.

1. Have each student draw the out- line of a shape that he or she observed on the walk. Share some of these with other members of the class. See if they can recall seeing this or a similar shape.

2. Have each student think of an object that is a certain shape because that shape helps the object do its job. A funnel would be a good example of this. Have the students sketch the shape of the object - maybe one or more of its faces or its cross-section. Each student can write what his or her object is and how its shape is useful in performing its job. Share the sketches with the class and ask for other objects for which a particular shape would be well-suited. For instance, an acute isos- celes triangle could represent not only the cross-section of a funnel (fig. la) but also an ice scraper (fig. 1b), a bicycle seat (fig. 7c), or the head of a rake (fig. Id).

3. Your students might also specu-

late about what shape or shapes an object might be if it were to perform a stated function. For example, you might ask students to sketch the design of a new and different fingernail file, doorknob, desktop or window, and write why they chose the shape they did. It might be interesting to see if they come up with some function- shape relationships that have already been found quite useful - the triangle for rigidity and stability, the circle for rolling and rotating, or the rectangle for tessellating or fitting together to cover a surface (fig. 8).

4. You might select a particular shape and ask students to use that shape, predominantly, to draw some- thing that looks pleasing to them. You could be more specific and ask them to sketch a design for a piece of sculpture, a piece of jewelry, a sign or, combining function and aesthetics, an attractive solar panel, piece of furniture, or eat- ing utensil. Allow them to choose the shapes they wish to use. Luckily, not everyone likes what someone else likes. Individual tastes may provide a variety of original creations that can be shared with the whole class. Ask the students which shapes they like best. Shapes may be associated with a product or event. A cone (or triangle), for instance, may remind one of an ice cream cone or a Christmas tree. Others may find just the shape alone appeal-

Fig. 8 I 1 1

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ing. You might show a golden rectangle (fig. 9), whose length is approxi- mately 1.6 times its width, and state that many people find this the most pleasingly-shaped rectangle. Or ask students to draw the rectangle that is most pleasing to them.

Fig. 9 I

5. Make a display of three or four bottles of different shapes and ask students which they find the most attractive. If the bottles all have the same ca- pacity, you might ask if any were designed so as to look as if they held more than others.

6. A geometric scavenger hunt could provide an opportunity to find objects that illustrate geometric terms. Groups of students could be given a list of terms and told to find and record the names of objects in the classroom that are examples of those terms. A rectangle, for example, could be found on the top of a table, a window, or a book. A circle could be seen in the face of a clock.

A geometry walk and the related activities should provide for your class some answers to the question, Why do we have to study geometry? And your students will begin to see that geometry can be relevant to everyday activities and interesting. D

Arithmetic Teacher



let's take a geometry walk

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