Go Math! Grade 3, Chapter 11: Perimeter and Area
In this unit, your child learns two different ways to measure a shape. Perimeter is the distance around it, found by adding side lengths. Area is the flat space it covers, found by counting square units or multiplying length by width. They compare rectangles with the same perimeter but different areas. Time and measuring come next.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Chapter 11?
- Seeing area as the number of unit squares that cover a shape, and keeping it separate from the distance around. Learn more: Area: how much flat space a shape covers
- Counting unit squares to find area, and naming the answer in square units like square centimeters. Learn more: Finding area by counting squares
- Multiplying length by width for rectangles and adding the parts of combined rectangles to find the whole area. Learn more: Finding the area of a rectangle
- Finding perimeter by adding sides, finding a missing side, and comparing rectangles with the same perimeter but different areas. Learn more: Perimeter: the distance around a shape
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
You want to cover a rectangular garden with new grass. Which measurement tells you how much grass you need?
- Perimeter
- Length
- Area
How you can help
- Measure around a table in hand spans for its perimeter, then cover its top with sheets of paper and count them for its area.
- Use 16 crackers to build rectangles with the same area, like 2 by 8 and 4 by 4, then compare the distance around each (20 and 16).
- Ask how many squares are in a chocolate bar or sheet of stickers without counting each one, such as 3 rows of 8 making 24.
Where kids can get stuck
- Mixing up area and perimeter, adding the sides for area or multiplying them for perimeter.
- Adding the length and width just once, so a 7 by 2 rectangle gets a perimeter of 9 instead of 18.
- Labeling an area in inches instead of square inches, as if it were a length.
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
- perimeter
- The total length of all the sides of a shape.
- area
- The space inside a flat shape, measured in squares.
- square unit
- The unit we use to measure area.
- unit square
- A square 1 unit on each side, used to measure area.
- length
- How long one side of a shape is.
- width
- How wide a shape is; the length of its other side.
- side length
- How long one side of a shape is.
- rectilinear figure
- A shape made only of straight sides that meet at square corners.
Want to help your child master perimeter and area?
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 Go Math! Grade 3 Chapter 11 cover?
Go Math! Grade 3 Chapter 11 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.