5th Grade · Geometry
5.G.B.3: Know that a square has everything a rectangle has, because it is one
5.G.B.3 is a 5th 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
Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category. For example, all rectangles have four right angles and squares are rectangles, so all squares have four right angles.
In plain words
Know that a square has everything a rectangle has, because it is one.
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
Ines sorts tiles. She knows every rhombus has four sides of the same length. Which tile must also have four sides of the same length?
- A parallelogram tile
- A square tile
- A rectangle tile
Where students can get stuck
- Insisting a square is not a rectangle because rectangles have "two long sides and two short sides."
- Reversing the reasoning, so they say all rectangles have four equal sides because squares do.
- Forgetting that a rectangle is a parallelogram, so its parallel, equal opposite sides come as a surprise.
Effective teaching strategies
- List the properties of a rectangle with students, such as four square corners and equal opposite sides, then test a square against each one.
- Draw nested boxes with squares inside rectangles inside parallelograms, and ask students what each outer shape passes on to the shapes inside it.
- Challenge the claim “all rectangles have four equal sides” by having students draw a rectangle that breaks it, so they see the reasoning only works one way.
Units that teach this standard
Find where 5.G.B.3 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
Into Math
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 Why a square is also a rectangle 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.