Bridges in Mathematics Grade 4, Unit 5: Geometry & Measurement
In this unit, your child explores angles and shapes. They learn that angles are measured in degrees, use a protractor, and add angles to find a missing one. They name lines, rays, and parallel and perpendicular lines; sort shapes by their sides and angles; and find lines of symmetry. Next, the year returns to multiplication, division, and fractions.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 5?
- Understanding an angle as a turn measured in degrees, with a full turn of 360 degrees and a quarter turn of 90. Learn more: What angles are and how degrees measure them
- Measuring angles to the nearest degree with a protractor, and drawing angles of a given size, like 65 degrees. Learn more: Measuring and drawing angles with a protractor
- Adding angles that sit side by side, and subtracting to find a missing angle inside a larger one. Learn more: Adding angles together to find a missing one
- Drawing and naming points, lines, line segments, rays, and right, acute, and obtuse angles; and spotting parallel and perpendicular lines. Learn more: Spotting lines, rays, angles, and parallel lines
- Sorting shapes by parallel sides, perpendicular sides, and angle size, and picking out right triangles. Learn more: Sorting shapes by their sides and angles
- Finding and drawing every line of symmetry on a shape, where it folds into two matching halves. 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
- Make angles with your arms and let your child name them: a square corner for a right angle, arms closer together for acute, and wider apart for obtuse.
- Look for parallel and perpendicular lines on a walk, like sidewalk edges or where a wall meets the ground. Ask your child to point out a right angle and explain how they know.
- Fold a square napkin every way the edges match. Ask your child to predict how many folds will work before trying, then count the four lines of symmetry together.
Where kids can get stuck
- Calling an angle bigger because its rays are longer, instead of checking how wide it opens.
- Reading the wrong row of numbers on a protractor, so a 50-degree angle is recorded as 130.
- Drawing a rectangle's diagonal as a line of symmetry, even though the halves do not match when folded.
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.
- ray
- A part of a line that starts at one point and goes on forever in one direction.
- parallel lines
- Lines that always stay the same distance apart and never meet.
- perpendicular lines
- Lines that meet or cross to make 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.
Want to help your child master angles and shapes?
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 Bridges in Mathematics Grade 4 Unit 5 cover?
Bridges in Mathematics Grade 4 Unit 5 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.