Let’s solve each part step by step.
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Section A: Right angles (90° total)
In a right angle, the two smaller angles add up to 90°.
1.
a°:
Given one angle is 25°, so:
a° = 90° - 25° =
65°
2.
b°:
One angle is 15°, so:
b° = 90° - 15° =
75°
3.
c°:
One angle is 80°, so:
c° = 90° - 80° =
10°
4.
d°:
One angle is 72°, so:
d° = 90° - 72° =
18°
5.
e°:
One angle is 34°, so:
e° = 90° - 34° =
56°
6.
f°:
One angle is 79°, so:
f° = 90° - 79° =
11°
✔ Section A done!
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Section B: Straight lines (180° total)
On a straight line, all angles together make 180°.
7.
g°:
One angle is 45°, so:
g° = 180° - 45° =
135°
8.
h°:
One angle is 128°, so:
h° = 180° - 128° =
52°
9.
i°:
One angle is 104°, so:
i° = 180° - 104° =
76°
10.
j°:
Two angles given: 71° and 48° → sum = 71 + 48 = 119°
j° = 180° - 119° =
61°
11.
k°:
There’s a right angle (90°) and an 11° angle.
So k° = 180° - 90° - 11° =
79°
12.
l°:
One angle is 43°, so:
l° = 180° - 43° =
137°
13.
m°:
Three angles on a straight line: 25°, m°, and 78°
Sum of knowns: 25 + 78 = 103°
m° = 180° - 103° =
77°
14.
n°:
Right angle (90°) and 16° are shown.
n° = 180° - 90° - 16° =
74°
15.
p°:
Right angle (90°) and 66° are shown.
p° = 180° - 90° - 66° =
24°
16.
q°:
Three equal angles labeled q° on a straight line → 3 × q° = 180°
So q° = 180° ÷ 3 =
60°
✔ All solved!
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Final Answer:
a° = 65
b° = 75
c° = 10
d° = 18
e° = 56
f° = 11
g° = 135
h° = 52
i° = 76
j° = 61
k° = 79
l° = 137
m° = 77
n° = 74
p° = 24
q° = 60
Parent Tip: Review the logic above to help your child master the concept of finding unknown angles worksheet.
