Who am I?
I have three equal sides and three equal angles. All my angles are 60°.
Equilateral Triangle
Name the following triangle:
A triangle with sides of length 5 cm, 5 cm, and 8 cm.
Isosceles Triangle
A quadrilateral has four equal sides and four right angles. What is its name?
Square
Two angles add up to 90°. If one angle is 25°, what is the other angle?
90 – 25 = 65°
I have one right angle and two other angles that add up to 90°.
Right Angle Triangle
Name the following triangle: A triangle with angles 40°, 60°, and 80°.
Scalene Triangle
A quadrilateral has two pairs of parallel sides, but no right angles. What is its name?
Parallelogram
Two angles are supplementary. One angle is 110°. What is the other angle?
180 – 110 = 70°
I have two equal sides and two equal angles. Sometimes people call me a “roof shape.”
Isosceles Triangle
One angle of a triangle is 40° and another is 75°. What is the size of the third angle?
180 - 75 - 40 = 65o
The angles in a quadrilateral are 90°, 85°, and 120°. What is the size of the fourth angle?
Angle sum of quadrilateral = 360°
90 + 85 + 120 = 295
360 – 295 = 65°
A straight line is split into two angles. One is 67°. Find the other.
Straight Angles → 180 – 67 = 113°
I have four equal sides, opposite sides parallel, but no right angles.
Rhombus
A triangle has two equal sides. One of the angles at the base is 35°. Find the other two angles.
180° – (35° + 35°) = 110°.
A quadrilateral has three angles measuring 100°, 80°, and 75°. What is the size of the fourth angle?
100 + 80 + 75 = 255
360 – 255 = 105°
Two angles are complementary. One angle is 38°. What is the other angle?
Answer: 90 – 38 = 52°
I have one pair of parallel sides. I can look like a ramp or a bridge.
Trapezium
In a right-angled triangle, one of the other angles is three times the size of the smallest angle. Find all three angles.
Right-angled triangle → one angle = 90°.
Let the smallest angle = x.
Other acute angle = 3x.
Equation: x + 3x + 90 = 180 → 4x = 90 → x = 22.5°.
So the angles are: 22.5°, 67.5°, 90°.
In a kite, one pair of opposite angles is 70° and 70°. Find the other two angles.
70 + 70 = 140
360 – 140 = 220
220 ÷ 2 = 110
So the angles are 70°, 70°, 110°, 110°
Three angles meet at a point to create a revolution. The first is 120° and the second is 95°. What is the third angle?
Angles around a point = 360°
120 + 95 = 215
360 – 215 = 145°