Explore · MATH-5B-C11-L01-OPEN
An angle is marked 37°. Classify it as acute, right, or obtuse; explain your classification.
Great Inheritance Mathematics Term B · Original independent course
Measuring Angles
Watch for: Reading the wrong protractor number ring.. Explain what the quantities mean before calculating.
Opening task
Prerequisite check
Before instruction · MATH-5B-C11-L01-PREREQ
How many degrees is a right angle?
Show worked answer (after attempting)
Answer: 90°
One right-angle turn is 90 degrees.
Understand the idea
Measure and draw angles with a protractor in degrees using the correct starting ray and scale. The essential earlier idea is: 4B angle terms, perpendicular lines and degree benchmarks.. The model below will always use the actual quantities from the worked problem. Check reading the wrong protractor number ring when you explain your answer.
Three worked examples
Worked example 1 · MATH-5B-C11-L01-Q01
An angle is marked 35°. Classify it as acute, right, or obtuse; explain your classification.
Solution: 35°, acute
For classification compare 35° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 35°.
Worked example 2 · MATH-5B-C11-L01-Q02
Draw a ray pair with an angle of 90° using a protractor. Explain which scale to read.
Solution: 90°, right
For classification compare 90° with 90° and 180°. The angle is right. For construction place the protractor center at the vertex, align zero with the starting ray and mark 90°.
Worked example 3 · MATH-5B-C11-L01-Q03
Classify an angle measuring 128° and explain.
Solution: 128°, obtuse
For classification compare 128° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 128°.
Check understanding
1 · MATH-5B-C11-L01-Q04
An angle is marked 37°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 37°, acute
For classification compare 37° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 37°.
2 · MATH-5B-C11-L01-Q05
Draw a ray pair with an angle of 92° using a protractor. Explain which scale to read.
Show worked answer (after attempting)
Answer: 92°, obtuse
For classification compare 92° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 92°.
3 · MATH-5B-C11-L01-Q06
Classify an angle measuring 130° and explain.
Show worked answer (after attempting)
Answer: 130°, obtuse
For classification compare 130° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 130°.
Guided practice
1 · MATH-5B-C11-L01-Q07
An angle is marked 39°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 39°, acute
For classification compare 39° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 39°.
2 · MATH-5B-C11-L01-Q08
Draw a ray pair with an angle of 94° using a protractor. Explain which scale to read.
Show worked answer (after attempting)
Answer: 94°, obtuse
For classification compare 94° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 94°.
3 · MATH-5B-C11-L01-Q09
Classify an angle measuring 132° and explain.
Show worked answer (after attempting)
Answer: 132°, obtuse
For classification compare 132° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 132°.
4 · MATH-5B-C11-L01-Q10
An angle is marked 41°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 41°, acute
For classification compare 41° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 41°.
Independent practice
1 · MATH-5B-C11-L01-Q11
Draw a ray pair with an angle of 96° using a protractor. Explain which scale to read.
Show worked answer (after attempting)
Answer: 96°, obtuse
For classification compare 96° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 96°.
2 · MATH-5B-C11-L01-Q12
Classify an angle measuring 134° and explain.
Show worked answer (after attempting)
Answer: 134°, obtuse
For classification compare 134° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 134°.
3 · MATH-5B-C11-L01-Q13
An angle is marked 43°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 43°, acute
For classification compare 43° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 43°.
4 · MATH-5B-C11-L01-Q14
Draw a ray pair with an angle of 98° using a protractor. Explain which scale to read.
Show worked answer (after attempting)
Answer: 98°, obtuse
For classification compare 98° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 98°.
5 · MATH-5B-C11-L01-Q15
Classify an angle measuring 136° and explain.
Show worked answer (after attempting)
Answer: 136°, obtuse
For classification compare 136° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 136°.
6 · MATH-5B-C11-L01-Q16
An angle is marked 45°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 45°, acute
For classification compare 45° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 45°.
7 · MATH-5B-C11-L01-Q17
Draw a ray pair with an angle of 100° using a protractor. Explain which scale to read.
Show worked answer (after attempting)
Answer: 100°, obtuse
For classification compare 100° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 100°.
8 · MATH-5B-C11-L01-Q18
Classify an angle measuring 138° and explain.
Show worked answer (after attempting)
Answer: 138°, obtuse
For classification compare 138° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 138°.
Challenge and error analysis
1 · MATH-5B-C11-L01-ERR1
The assigned question is: “Draw a ray pair with an angle of 106° using a protractor. Explain which scale to read.” A learner wrote: “I classified or constructed the angle of 106 degrees without measuring from the aligned zero ray; I reported 106.1°, obtuse.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.
Show worked answer (after attempting)
Answer: Correct result: 106°, obtuse
The attempted reasoning or reported result does not satisfy the specified operation, units or geometric conditions. Correct mathematical result: 106°, obtuse. Recompute from the given data: For classification compare 106° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 106°.
2 · MATH-5B-C11-L01-ERR2
The assigned question is: “Classify an angle measuring 144° and explain.” A learner wrote: “I classified or constructed the angle of 144 degrees without measuring from the aligned zero ray; I reported 145°, obtuse.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.
Show worked answer (after attempting)
Answer: Correct result: 144°, obtuse
The attempted reasoning or reported result does not satisfy the specified operation, units or geometric conditions. Correct mathematical result: 144°, obtuse. Recompute from the given data: For classification compare 144° with 90° and 180°. The angle is obtuse. For construction place the protractor center at the vertex, align zero with the starting ray and mark 144°.
Exit check
Exit · MATH-5B-C11-L01-Q19
An angle is marked 47°. Classify it as acute, right, or obtuse; explain your classification.
Show worked answer (after attempting)
Answer: 47°, acute
For classification compare 47° with 90° and 180°. The angle is acute. For construction place the protractor center at the vertex, align zero with the starting ray and mark 47°.