Angle Measure Worksheet 1
1
2
1. In the figure above, lines a and b are parallel. If the measure of ∠1 is 145°, what is
the measure of ∠2 ?
A.
B.
C.
D.
25°
35°
45°
145°
x°
129°
94°
2. In the figure above, what is x ?
A. 35
B. 43
C. 51
D. 86
nA = 360
3. The measure A, in degrees, of an exterior angle of a regular polygon is related to
the number of sides, n, of the polygon by the formula above. If a regular polygon has
between 4 and 6 sides, inclusive, which of the following could be the measure of an
exterior angle of the polygon?
A. 40°
B. 45°
C. 60°
D. 120°
ANSWERS
1B
2B
3C
EXPLANATIONS
QUESTION 1
1. Fill in missing angle measures:
180° on one side of a line:
angle 1 + the small angle down and to the right of it = 180°
the small angle = 35°
parallel lines:
since lines a and b are parallel, intersecting line c creates equal angles:
angle 2 = the small angle down and to the right of angle 1
angle 2 = 35°
QUESTION 2
1. Fill in missing angle measures:
180° on one side of a line:
129° + the small angle to the right of it = 180°
the small angle = 51°
94° + the small angle above it = 180°
the small angle = 86°
180° in a triangle:
51° + 86° + top angle inside triangle = 180°
top angle inside triangle = 43°
where lines cross, angles opposite each other are equal:
x = 43
QUESTION 3
1. Fill in missing angle measures:
To find a possible exterior angle, pretend the regular polygon has 4 sides. Plug 4 in
for n in the formula given:
(4)A = 360
à
A = 90
90 isn’t an answer choice, so pretend the regular polygon has 5 sides. Plug 5 in for n
in the formula given:
(5)A = 360
à
A = 52
52 isn’t an answer choice, so pretend the regular polygon has 6 sides. Plug 6 in for n
in the formula given:
(6)A = 360
à
A = 60