Download Triangle Math Grade 5

Objectives:
• After completing this activity you will be able to identify
triangles by their angles and their side lengths.
•After completing this activity you will be able to identify
two triangles as congruent.
Are you ready? Click on the house to continue to the main menu.
This button will return you to the main menu at any point. Let’s go!
Created by Ruth Myles
CEP 811
Menu
 Identifying triangles by angle size
 Identifying triangles by length
 Identifying triangles as congruent
 Practice
Angle sizes
Stop and Think!
What do you notice about these angles?
Continue
Did you notice that these angles are all
small? We call angles that are less than
90 degrees acute. You can remember
this by thinking of “a cute” little angle.
Notice how the 90 degree angle looks
like a chair? This angle is called a right
angle. Any angle that is smaller than
that chair is our acute little angle!
Right Angle- 90 degrees
Acute Angle- Less than
90 degrees
.
Remember:
90 degree angles are chairs, they are “right” to sit on.
Acute angles are less than 90 degrees, they are “ a cute” little angle
Stop and Think!
Do you know what we call the last angle?
Right Angle
Acute Angle
????
Obtuse Angles
Any angle larger than 90 degrees is called obtuse. Can you think of a way to
remember that the obtuse angle is a big angle?
Right Angle- 90 degrees
Obtuse angle- More than 90 degrees
Let’s look at some examples!
(Click to check your work)
Can you figure out which 2 arrows are
pointing to obtuse angles?
Let’s look at some examples!
Can you figure out which 2 arrows are
pointing to acute angles?
Let’s look at some examples!
Can you figure out which 3 arrows are
pointing to right angles?
Triangles
Angle sizes help us to identify triangles too!
Look at the triangles below, and see if you can guess what
kind of triangle they are:
Click the triangles to check your work
Great Job!
Use the home button to choose
a new topic or to start the
practice session.
Triangle Side Length
You already know that we can name triangles by their
angles…. Did you know we can name them by their side
length too?
Look at this triangle and think about what’s special about it.
Maybe you noticed…
What about the sides of the
triangle?
 It’s blue
 It’s an acute
triangle
 The angles are all
the same size
When all the sides of a triangle
are the same or equal we call
it an equilateral triangle!
What if all the sides are not equal?
This triangle has two equal sides.
It is called an isosceles triangle.
Some students think they look
like icicles.
This triangle has no sides that are
the same length. It is called a
scalene triangle. Can you think
of a way to remember that
scalene triangles have no
equal lengths?
Review
Can you tell what kind of triangles these are by looking at
the lengths of their sides? Click and listen to check your
work.
Use the home button to choose a new topic or to start the
practice session.
What does congruent mean?
Triangles are congruent if they are the same shape and size.
Are these triangles congruent?
We can tell if two triangles are congruent by
placing them on top of each other. If they match,
they are congruent.
These triangles are the same shape, but they are not the same
size. They are not congruent.
How else can we tell if triangles are
congruent?
We can’t always place two shapes on top of each other. Can you
think of another way of telling if these triangles are
congruent?
1.5 inches
Measure it!
2 in.
Looking at these measurements, we can tell that these triangles
are congruent! They are the same shape, and the same size.
Now it’s time to practice!
On the following pages answer the questions the best you
can. If you need to review a section, click on the home
button.
What kind of
triangle is this?
A. Obtuse
B. Acute
C. Equilateral
What kind of
triangle is this?
A. Right
B. Acute
C. Obtuse
What type of
triangle is this?
A. Scalene
B. Obtuse
C. Equilateral
What type of
triangle is this?
A. Isosceles
B. Scalene
C. Right
What type of
triangle is this?
A. Equilateral
B. Acute
C. Obtuse
What type of
triangle is this?
A. Equilateral
B. Scalene
C. Isosceles
What makes triangles congruent?
A. The angles in both triangles are the
same.
B. The shape of the triangle is the same.
C. The shape and size are the same.
Are these triangles congruent?
Why?
A. Yes, because they are
the same shape.
B. No, because they are
different colors.
C. No, they are different
sizes.
Are these triangles congruent?
Why?
A. No, they are different
colors.
B. No, they are facing
different directions.
C. Yes, they are the same
shape and size.
1 inch
Can you
find the
acute
equilateral
triangle?
Can you
find the
right
scalene
triangle?
Can you find
the obtuse
isosceles
triangle?
Can you
find the
acute
isosceles
triangles?