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Teacher Key
Geometry
Properties of Shapes
Triangles
Name each triangle according to its angles.
A.
B.
acute triangle
C.
right triangle
obtuse triangle
Name each triangle according to its side lengths.
D.
E.
scalene triangle
F.
equilateral triangle
isosceles triangle
Word Bank
Draw a triangle with more than 1 name. List the names.
acute
equilateral
Names
a. acute and
equilateral
b. right and
isosceles
© 2002 CompassLearning, Inc.
Answers may vary. Two
possible solutions are shown
below.
a.
b.
Triangles
isosceles
obtuse
right
scalene
Activity 40832
40833
Teacher Key
Geometry
Properties of Shapes
Triangles
Divide each shape 1 time to form congruent triangles. Name the types of triangles
created.
Answers may vary.
G.
H.
right or isosceles
triangles
I.
right or scalene
triangles
right or scalene
triangles
Divide each shape to form 4 congruent triangles. Name the types of triangles created.
J.
K.
right or isosceles
triangles
L.
right or scalene
triangles
acute or equilateral
triangles
Can an equilateral triangle also be a right triangle? Explain your thinking.
No, an equilateral triangle cannot be a right angle. In order for the
sides of a triangle to be equal in length, the angles must also be
equal. This results in 3 acute angles for an equilateral triangle.
Note: An isosceles triangle may be a right triangle.
© 2002 CompassLearning, Inc.
Activity 40832
40833
Teacher Key
Geometry
Properties of Shapes
Connections
Today I learned:
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Explore
Can an equilateral triangle also be an obtuse triangle? Can a scalene triangle also be
an acute triangle? Discover the answers to these questions and more by using a few
materials and completing the chart below.
You will need plastic straws, yarn, scissors, and a ruler.
Cut 3 pieces of yarn 24” long.
Cut the plastics straws into the following lengths: 2”, 3”, 4”, 5”, 6”, 7”, and 8”.
Make 3 sets in all.
Using the straw pieces as sides of triangles, create triangles to help you complete the
chart. Thread together 3 straws. Bring the ends of the yarn together to form a triangle.
Place an O if both types of triangles can be made from the same straw pieces. Place
an X if both triangles cannot be made.
Acute Triangle Right Triangle Obtuse Triangle
Equilateral Triangle
O
X
X
Isosceles Triangle
O
O
O
Scalene Triangle
O
O
O
© 2002 CompassLearning, Inc.
Activity 40832
40833