4th Grade · Geometry
4.G.A.2: Sort shapes by their parallel sides and right angles
4.G.A.2 is a 4th grade Common Core math standard in Geometry. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.
In plain words
Sort shapes by their parallel sides and right angles.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
Sofia draws a triangle with angles of 90°, 50° and 40°. What kind of triangle is it?
- An obtuse triangle
- A right triangle
- An acute triangle
Where students can get stuck
- Deciding a triangle is not a right triangle because it is turned so the square corner is not at the bottom.
- Leaving a square out of the group with parallel sides or right angles, because it already has its own name.
- Calling two sides parallel because they look close, without checking that they stay the same distance apart.
Effective teaching strategies
- Sort figure cards by whether they have parallel sides, right angles, both, or neither, and ask where a square belongs and why.
- Turn right triangle cards in different directions and ask students to find the square corner each time, so they see the triangle stays a right triangle.
- Ask students to check suspected parallel sides by measuring the distance between them at two spots with a ruler and confirming it is the same.
Units that teach this standard
Find where 4.G.A.2 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Sorting shapes by their sides and angles for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice geometry at home
In Bobby's Math Club, students practice 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 for every family.
See how it works for teachers
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.