Name:
Triangles Print Activity
Watch the Video Interactive step by step to answer all of the following questions.
1.
The following is a copy of the first diagram from the Video Interactive. Answer
the Questions by filling in the blanks.
a.
All 3 interior angles of any triangle add up

to
.
b.
Opposite angles are always
c.
x = _______ 
y = _______ 
.
2.
Suppose that each given angle in the first diagram from the Video Interactive
was changed to 50  (as shown in the following diagram). Find the new values of
x and y.
50
50
x = _______ 
y = _______ 
50
50
3.
The following is a copy of the second diagram from the Video Interactive. Find
the values of x and y.
x = _______ 
y = _______ 
4.
Suppose that the given angles in the second diagram from the Video Interactive
were changed to 60  and 58  (as shown). Find the new values of x and y.
60
60
58
58
x = _______ 
y = _______ 
Junior High Math Interactives
2005 Alberta Education (www.LearnAlberta.ca)
Shape and Space / Triangles / Video Interactive / Print Activity
Page 1 of 4
5.
6.
The following is a copy of the third diagram from the Video Interactive. Answer
the questions by filling in the blanks.
a.
Two angles that add up to 180 are called
______________ angles.
b.
x = _______ 
y = _______ 
Suppose that the given angle in the third diagram from the Video Interactive was
changed to 38  (as shown). Find the new values of x and y.
x = _______ 
y = _______ 
38
7.
The following is a copy of the fourth diagram from the Video Interactive. Find
the values of x, y and z.
x = _______ 
y = _______ 
z = _______ 
8.
Suppose the given angle in the fourth diagram from the Video Interactive was
changed to 35  (as shown). Find the new values of x, y and z.
35
x = _______ 
y = _______ 
z = _______ 
Junior High Math Interactives
2005 Alberta Education (www.LearnAlberta.ca)
Shape and Space / Triangles / Video Interactive / Print Activity
Page 2 of 4
9.
10.
The following is a copy of the fifth diagram from the Video Interactive. Answer
the questions by filling in the blanks.
a.
Two angles that add up to 90 are called
______________ angles.
b.
x = _______ 
y = _______ 
z = _______ 
Suppose that the given angles in the fifth diagram from the Video Interactive
were changed to 35  and 105  (as shown). Find the new values of x, y and z.
35
x = _______ 
y = _______ 
z = _______ 
105
11.
The following is a copy of the sixth diagram from the Video Interactive. Find the
values of x and y.
x = _______ 
y = _______ 
12.
Suppose that the given angles in the sixth diagram from the Video Interactive
were both changed to 60  (as shown). Find the new values of x and y.
60
60
y
x = _______ 
y = _______ 
Junior High Math Interactives
2005 Alberta Education (www.LearnAlberta.ca)
Shape and Space / Triangles / Video Interactive / Print Activity
Page 3 of 4
13.
The following is a copy of the seventh diagram from the Video Interactive. Find
the values of x and y.
x = _______ 
y = _______ 
14.
Suppose that the given angles in the seventh diagram from the Video Interactive
were changed to 80  and 100  (as shown). Find the new values of x and y.
x
80 100
y
x = _______ 
y = _______ 
x y
15.
Find the values of x and y in each of the following diagrams.
Then, choose the best reason for determining their values from the list.
A.
B.
C.
D.
Reasons
All 3 interior angles of a triangle add up to 180 .
Opposite angles are equal.
Complementary angles add up to 90 .
Supplementary angles add up to 180 .
a.

, Reason =

, Reason =
x=

, Reason =
y=

, Reason =
x=
y=
20 
x
y
b.
x
25 
y
130 
Junior High Math Interactives
2005 Alberta Education (www.LearnAlberta.ca)
Shape and Space / Triangles / Video Interactive / Print Activity
Page 4 of 4