3B · Chapter 12 · exam
Chapter practice examination
Original untimed practice examination. Not a secure or official placement test.
Original untimed practice examination. Not a secure or official placement test. Solutions are available as revealable feedback and in a separate complete answer key. No answer submissions or accounts are required.
Assessment · 24 questions
Questions
Show your thinking; use diagrams when they help. Do not open solutions during your first attempt.
- A1
A student answers the following question with “scalene”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: A triangle has side lengths 11, 11, and 13 units. Classify it by its side lengths. (3 points)
Reveal explanation
Answer: isosceles
The suggested answer is not correct. Isosceles means exactly two equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
- A2
An angle measures 139°. Is it acute, right, or obtuse? (2 points)
Reveal explanation
Answer: obtuse
Compare 139° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
Angle of 139 degrees; angle size depends on rotation, not ray length. - A3
Using a compass set to 22 mm, draw a circle. What must be the distance from the center to every point on the circle? (3 points)
Reveal explanation
Answer: 22 mm
The fixed compass opening is the radius. Keep its needle fixed and rotate the pencil to keep every perimeter point 22 mm from the center.
Scoring: 1 point for the center, 1 for the accurate radius, 1 for a complete labeled circle.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A4
A circle has diameter 32 cm. What is its radius? (2 points)
Reveal explanation
Answer: 16 cm
The radius is half the diameter. 32 ÷ 2 = 16 cm.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A5
A student answers the following question with “obtuse”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: An angle measures 50°. Is it acute, right, or obtuse? (3 points)
Reveal explanation
Answer: acute
The suggested answer is not correct. Compare 50° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
Angle of 50 degrees; angle size depends on rotation, not ray length. - A6
A triangle has side lengths 5, 5, and 5 units. Classify it by its side lengths. (2 points)
Reveal explanation
Answer: equilateral
Equilateral means three equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
- A7
A triangle has side lengths 3, 4, and 5 units. Classify it by its side lengths. (2 points)
Reveal explanation
Answer: scalene
Scalene means no equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
- A8
A triangle has side lengths 14, 14, and 16 units. Classify it by its side lengths. (2 points)
Reveal explanation
Answer: isosceles
Isosceles means exactly two equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
- A9
A student answers the following question with “scalene”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: A triangle has side lengths 13, 13, and 13 units. Classify it by its side lengths. (3 points)
Reveal explanation
Answer: equilateral
The suggested answer is not correct. Equilateral means three equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
- A10
A triangle has side lengths 10, 10, and 12 units. Classify it by its side lengths. (2 points)
Reveal explanation
Answer: isosceles
Isosceles means exactly two equal sides. These lengths satisfy the triangle inequality.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
- A11
An angle measures 42°. Is it acute, right, or obtuse? (2 points)
Reveal explanation
Answer: acute
Compare 42° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
Angle of 42 degrees; angle size depends on rotation, not ray length. - A12
Using a compass set to 9 mm, draw a circle. What must be the distance from the center to every point on the circle? (3 points)
Reveal explanation
Answer: 9 mm
The fixed compass opening is the radius. Keep its needle fixed and rotate the pencil to keep every perimeter point 9 mm from the center.
Scoring: 1 point for the center, 1 for the accurate radius, 1 for a complete labeled circle.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A13
A student answers the following question with “acute”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: An angle measures 101°. Is it acute, right, or obtuse? (3 points)
Reveal explanation
Answer: obtuse
The suggested answer is not correct. Compare 101° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
Angle of 101 degrees; angle size depends on rotation, not ray length. - A14
An angle measures 31°. Is it acute, right, or obtuse? (2 points)
Reveal explanation
Answer: acute
Compare 31° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
Angle of 31 degrees; angle size depends on rotation, not ray length. - A15
Identify the most specific shape: a quadrilateral has four right angles, adjacent side lengths 9 cm and 11 cm. (2 points)
Reveal explanation
Answer: rectangle
The shape is a rectangle. Check right angles, equal-length sides and parallel lines; the description distinguishes it from the other listed types.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
- A16
Using a compass set to 21 mm, draw a circle. What must be the distance from the center to every point on the circle? (3 points)
Reveal explanation
Answer: 21 mm
The fixed compass opening is the radius. Keep its needle fixed and rotate the pencil to keep every perimeter point 21 mm from the center.
Scoring: 1 point for the center, 1 for the accurate radius, 1 for a complete labeled circle.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A17
A student answers the following question with “rhombus with no right angles”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: Identify the most specific shape: a quadrilateral has four right angles and four equal sides of 5 cm. (3 points)
Reveal explanation
Answer: square
The suggested answer is not correct. The shape is a square. Check right angles, equal-length sides and parallel lines; the description distinguishes it from the other listed types.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
- A18
A circle has diameter 44 cm. What is its radius? (2 points)
Reveal explanation
Answer: 22 cm
The radius is half the diameter. 44 ÷ 2 = 22 cm.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A19
An angle measures 78°. Is it acute, right, or obtuse? (2 points)
Reveal explanation
Answer: acute
Compare 78° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
Angle of 78 degrees; angle size depends on rotation, not ray length. - A20
An angle measures 165°. Is it acute, right, or obtuse? (2 points)
Reveal explanation
Answer: obtuse
Compare 165° with 90°: angles smaller are acute, exactly 90° are right, and larger but less than 180° are obtuse.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
Angle of 165 degrees; angle size depends on rotation, not ray length. - A21
A student answers the following question with “10 cm”. Explain whether the answer is correct, then solve the question and justify your answer. Original question: A circle has diameter 18 cm. What is its radius? (3 points)
Reveal explanation
Answer: 9 cm
The suggested answer is not correct. The radius is half the diameter. 18 ÷ 2 = 9 cm.
Scoring: 1 point for identifying the given answer as incorrect; 1 for explaining the error; 1 for giving the corrected solution and appropriate units.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A22
A circle has radius 24 cm. What is its diameter? (2 points)
Reveal explanation
Answer: 48 cm
A diameter joins two radii end to end through the center: 24 + 24 = 48 cm.
Scoring: 1 point for a mathematically valid calculation/model, 1 point for the correct final answer with units when appropriate.
The radius runs from center to edge. The diameter crosses the center from edge to edge. - A23
An angle is 60°. A student calls it obtuse because the rays look long. Explain the error. (3 points)
Reveal explanation
Answer: Acute
60° is below 90°, so the angle is acute; ray length is irrelevant.
Scoring: 1 point for the correct claim; 1 for a mathematical justification; 1 for a clear diagram, example, or relevant calculation when applicable.
- A24
Two circles have diameters 10 cm and 12 cm. Which has the larger radius and by how much? (3 points)
Reveal explanation
Answer: Second circle, by 1 cm
Their radii are 5 cm and 6 cm; changing diameter by 2 cm changes radius by 1 cm.
Scoring: 1 point for the correct claim; 1 for a mathematical justification; 1 for a clear diagram, example, or relevant calculation when applicable.