Unit 5
A C T I V I T Y 27
AC TIVIT Y
Symmetry
Use after
Unit 5, Session 3.5
Vocabulary/Vocabulario
line of symmetry/
eje de simetría
mirror image/
imagen reflejada
reflection symmetry/
simetría de reflexión
rotational symmetry/
simetría rotacional
Materials/Materiales
• scissors/
tijeras
• Power Polygons™/
polígonos Power
• Activity 27 Master (see below)/
Actividad 27 (ver abajo)
CVbZ
Un i t 5
Activity 27
MASTER
9ViZ
Measuring Polygons
NOTE Students draw and identify
shapes with reflection and rotational
symmetry and identify lines of symmetry.
OCC;JHO
& 9gVlVÄ\jgZl^i]gZÅZXi^dc
hnbbZignVcYYgVlVcn
a^cZhd[hnbbZign#
i]ZÄ\jgZ#
HiViZ^[i]ZÄ\jgZ]VhgZÅZXi^dchnbbZign!gdiVi^dcVa
hnbbZign!dgWdi]#>[i]ZÄ\jgZ]VhgZÅZXi^dchnbbZign!
YgVli]Za^cZhd[hnbbZign#
© Pearson Education, Inc. 5
GROUPS
Have students fold a piece of paper in half vertically. Have them
begin at the top left corner at the fold line to draw two sides of a
triangle as shown. The fold line will serve as the third side of the
triangle. Then have students cut out the resulting triangle and unfold
the paper to show one large triangle.
The fold line is a line of symmetry for the large triangle. This
means that the large triangle can be folded into two congruent
parts that can exactly fit on top of each other. We say that each
of the smaller triangles is a mirror image of the other because
one triangle can be reflected onto the other. We say that the large
triangle has reflection symmetry.
Let’s explore if a figure can have more than one line of symmetry. Remember, any
fold line that would result in two congruent parts that fit on top of each other is a
line of symmetry.
Give each student a square piece of paper and draw a square on the
board. How many lines of symmetry can you find in the square?
Draw them on the board. Students should be able to come up with
four lines of symmetry.
Distribute Power Polygons to each group of students. Have them trace the rectangle
block on a sheet of paper. Then, with the block on the drawing, have students begin
rotating it, counting how many times, if any, the block coincides with the drawing
before the block is back in its original position. It may help to keep one finger on a
particular vertex to remember the original orientation of the block.
' 9gVli]Za^cZd[hnbbZign[dg
( 25 MIN
) A figure that rotates onto itself in less than one full turn has rotational symmetry.
Does the rectangle have rotational symmetry? Have students experiment with
the other shapes from the Power Polygons. Students should conclude that the shapes
with rotational symmetry include the hexagon, square, parallelogram, rhombus, and
equilateral triangle (as well as the rectangle). Name some real-world objects that have
rotational symmetry.
C
* +
M
© Pearson Education, Inc. 5
Use after Unit 5, Session 3.5
Mention that some figures have both reflection and rotational symmetry. A square is
such a figure. Which of the Power Polygons have both types of symmetry? Students
should conclude that the hexagon, square, rectangle, rhombus, and equilateral triangle
all do. The parallelogram has only rotational symmetry.
PR AC TICE
In the Activity 27 Master, students will draw and identify shapes with reflection and
rotational symmetry and identify lines of symmetry.
DIFFERENTIATION : Suppor ting the Range of Learner s
Display the alphabet in capital block letters. Have the students classify
the letters into those that have reflection symmetry, those that have rotational symmetry,
those that have both types of symmetry, and those that have neither type of symmetry.
Unit 5: Measuring Polygons
Session 3.5 (End-of-Unit Assessment)