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Rule for a Missing Angle on the Triangle

Level 1

This math topic focuses on determining the relationships between angles in triangles, specifically within the context of geometry involving isosceles and equilateral triangles. It challenges students to use the triangle angle sum rule, where the total degrees in a triangle sum up to 180 degrees, to identify correct angle relationships and solve for missing angles, denoted by variables like x, y, z, b, d, n, and m. Each question presents a triangle with some angle values given and asks the student to identify the correct statement about the sum of the angles or the relationship between them.

Work on practice problems directly here, or download the printable pdf worksheet to practice offline.

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Rule for a Missing Angle on the Triangle Worksheet

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Rule for a Missing Angle on the Triangle
1
An svg image showing a math problem
What is known about the angles labelled 30, 60, r
a
30 is the same as 60
b
r and 60 add to 30
c
30 and 60 add to r
d
30 is half 60
e
30, 60, and r add up to 180°
f
30 and 60 add to twice r
2
An svg image showing a math problem
What is known about the angles labelled 70, 50, m
a
70 and 50 add to m
b
Nothing, 70, 50, and m are not related by any geometry rule
c
70 and 50 add to twice m
d
m and 50 add to 70
e
70, 50, and m add up to 180°
f
70, 50, and m add up to 90°
3
An svg image showing a math problem
What is known about the angles labelled 55, 73, p
a
55 and 73 add to p
b
55 is the same as 73
c
55, 73, and p add up to 180°
d
55, 73, and p add up to 360°
e
p and 73 add to 55
f
Nothing, 55, 73, and p are not related by any geometry rule
4
An svg image showing a math problem
What is known about the angles labelled 45, 45, z
a
45, 45, and z add up to 90°
b
45 and 45 add to z
c
45, 45, and z add up to 180°
d
45 is the same as 45
e
45, 45, and z add up to 360°
f
Nothing, 45, 45, and z are not related by any geometry rule
5
An svg image showing a math problem
What is known about the angles labelled 42, 35, c
a
Nothing, 42, 35, and c are not related by any geometry rule
b
42, 35, and c add up to 180°
c
42 and 35 add to c
d
c and 35 add to 42
e
42, 35, and c add up to 360°
f
42, 35, and c add up to 90°
6
An svg image showing a math problem
What is known about the angles labelled 30, 50, n
a
30 is half 50
b
n and 50 add to 30
c
30, 50, and n add up to 180°
d
30, 50, and n add up to 360°
e
30 and 50 add to n
f
30 and 50 add to twice n
7
An svg image showing a math problem
What is known about the angles labelled 78, 35, m
a
78, 35, and m add up to 90°
b
78 is the same as 35
c
78 and 35 add to twice m
d
m and 35 add to 78
e
78, 35, and m add up to 180°
f
Nothing, 78, 35, and m are not related by any geometry rule
8
An svg image showing a math problem
What is known about the angles labelled 70, 70, y
a
70 is the same as 70
b
70 and 70 add to twice y
c
70, 70, and y add up to 180°
d
70, 70, and y add up to 90°
e
70, 70, and y add up to 360°
f
y and 70 add to 70