Angles and Measurement — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A triangle has angles of 40° and 70°. What is the third angle?
A) 60°
B) 70°
C) 80°
D) 90°
The correct answer is B) 70°. A triangle has angles of 40° and 70°. What is the third angle — the answer is 70°.
2. A quadrilateral has angles of 85°, 95°, and 110°. What is the fourth angle?
A) 60°
B) 70°
C) 80°
D) 90°
The correct answer is B) 70°. A quadrilateral has angles of 85°, 95°, and 110°. What is the fourth angle — the answer is 70°.
3. The hands of a clock at 4:00 form what angle?
A) 90°
B) 100°
C) 110°
D) 120°
The correct answer is D) 120°. The hands of a clock at 4:00 form what angle — the answer is 120°.
4. An isosceles triangle has a top angle of 40°. What does each base angle measure?
A) 60°
B) 70°
C) 80°
D) 140°
The correct answer is B) 70°. An isosceles triangle has a top angle of 40°. What does each base angle measure — the answer is 70°.
Part B: Fill in the Blank
Write the correct answer on each line.
1. The sum of all angles in any quadrilateral is 360 degrees.
Every quadrilateral can be split into two triangles, and each triangle's angles sum to 180°, so 180° + 180° = 360° total.
2. A triangle with angles 60°, 60°, and 60° is called an equilateral triangle.
When all three angles are equal at 60°, all three sides must also be equal, which is the definition of an equilateral triangle.
3. If a triangle has a right angle and a 50° angle, the third angle is 40 degrees.
A triangle's angles sum to 180°, so subtract the right angle (90°) and the 50° angle: 180° minus 90° minus 50° = 40°.
4. A square has four angles that each measure 90 degrees.
A square has four right angles by definition, and every right angle measures exactly 90°.
5. The hands of a clock at 12:30 form an angle of about 165 degrees.
At 12:30 the minute hand is at 6 (180°) and the hour hand has moved halfway between 12 and 1 (15°), so the angle is 180° minus 15° = 165°.