Zearn Math Grade 4, Mission 4: Angle Measure and Plane Figures
In this unit, your child learns the language of geometry: points, lines, rays, angles, and parallel and perpendicular lines. They measure and draw angles in degrees, find unknown angles, sort shapes by their sides and angles, and draw lines of symmetry. It follows multidigit multiplication and division and leads into fraction equivalence.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Mission 4?
- Recognizing angles as turns through a circle measured in degrees, with a right angle at 90 and a straight angle at 180. Learn more: What angles are and how degrees measure them
- Measuring and drawing angles of any size with a protractor, reading the scale that starts at 0 on the angle's first ray. Learn more: Measuring and drawing angles with a protractor
- Writing and solving equations to find unknown angles, such as the angle that joins a 40-degree angle to make a right angle. Learn more: Adding angles together to find a missing one
- Naming and drawing lines, rays, line segments, and right, acute, and obtuse angles, and spotting parallel and perpendicular lines. Learn more: Spotting lines, rays, angles, and parallel lines
- Classifying triangles and four-sided shapes by parallel and perpendicular sides and by angle size, including right triangles. Learn more: Sorting shapes by their sides and angles
- Folding and drawing to find lines of symmetry, and deciding which shapes have none, one, or several. Learn more: Finding lines of symmetry
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
- Fold a paper plate in half and then in half again, and talk with your child about how the folds mark a 180-degree angle and then a 90-degree angle.
- Look for symmetry on a walk or ride, in windows, signs, and doors, and ask your child where each one could fold into matching halves.
- Use the corner of an index card to test angles around the house, and have your child sort each one as acute, right, or obtuse.
Where kids can get stuck
- Reading the inner scale when the angle starts at the outer zero, so a 50-degree angle gets measured as 130.
- Calling two sides parallel because they look close, without checking that they stay the same distance apart.
- Missing a line of symmetry when a shape is tilted on the page, as if it must stand upright.
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 formed where two rays meet at the same endpoint.
- degree
- The unit for measuring angles; a full turn is 360 degrees.
- protractor
- A tool for measuring and drawing angles in degrees.
- ray
- Part of a line with one endpoint that goes on forever in one direction.
- parallel lines
- Lines that stay the same distance apart and never meet.
- perpendicular lines
- Lines that cross or meet to form right angles.
- right triangle
- A triangle with one right angle.
- line of symmetry
- A line that folds a shape into two halves that match exactly.
- vertex
- The point where the two rays of an angle meet.
Ready to build your child’s confidence with angles and plane figures?
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.
Join the club
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 Zearn Math Grade 4 Mission 4 cover?
Zearn Math Grade 4 Mission 4 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
- 4.MD.C.5: Understand angles as turns measured in degrees: a full turn is 360°.
- 4.MD.C.6: Measure angles in degrees with a protractor.
- 4.MD.C.7: Add angles together, and find a missing angle.
- 4.G.A.1: Name rays and angles, and spot parallel and perpendicular lines.
- 4.G.A.2: Sort shapes by their parallel sides and right angles.
- 4.G.A.3: Find lines of symmetry, where a shape folds into matching halves.
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.