enVision Mathematics Grade 4, Topic 15: Angle Measurement
In this unit, your child learns that an angle is measured by how far it turns, in degrees, with a full turn being 360 degrees. They measure and draw angles with a protractor, and add angles together to find a missing one. It builds on last unit's lines and angles, and leads into perimeter and area.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Topic 15?
- Seeing angles as parts of a circle, where a 1-degree angle is 1/360 of a full turn. Learn more: What angles are and how degrees measure them
- Lining up a protractor's center on the vertex to measure angles, and drawing angles of an exact size. Learn more: Measuring and drawing angles with a protractor
- Writing equations to find an unknown angle, like 90 − 35 = 55 when a right angle is split in two. Learn more: Adding angles together to find a missing one
Sample questions to try together
These are real questions from our practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
An angle measures 60°. How many one-degree angles does it turn through?
- 300
- 60
- 6
How you can help
- Open a door slowly together and talk about how much it turns. Opened to a square corner, it has turned about 90 degrees; halfway to that is about 45.
- Look at a clock together. Ask how far the minute hand turns from 12 to 3, then from 12 to 6, and connect them to 90 and 180 degrees.
- Fold the corner of a sheet of paper so the crease splits the 90-degree corner in two. Measure one part, and have your child predict the other before measuring.
Where kids can get stuck
- Measuring angles in inches or centimeters, as if the length of the rays were what counts.
- Placing the protractor's edge at the vertex instead of its center point, which throws every reading off.
- Subtracting from 180 instead of 90 for a right angle, answering 145 instead of 55.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- angle
- The figure made by two rays that share an endpoint.
- vertex
- The point where two rays or two sides meet.
- degree
- The unit for measuring angles; a full turn is 360 degrees.
- protractor
- A half-circle tool marked in degrees, used to measure and draw angles.
- right angle
- An angle that measures exactly 90 degrees, like the corner of a sheet of paper.
- acute angle
- An angle smaller than a right angle, measuring less than 90 degrees.
- obtuse angle
- An angle larger than a right angle but smaller than 180 degrees.
- straight angle
- An angle that measures 180 degrees and looks like a straight line.
Ready to build your child’s confidence with measuring angles?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
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Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
Which math standards does enVision Mathematics Grade 4 Topic 15 cover?
enVision Mathematics Grade 4 Topic 15 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.