Area & Perimeter | Teacher Guide

Florida B.E.S.T. Standards

MA.3.GR.2.1

Explore area as an attribute of a two-dimensional figure by covering the figure with unit squares without gaps or overlaps. Find areas of rectangles by counting unit squares.

Key Point: This is a conceptual foundation. Students physically cover shapes and COUNT squares before using formulas.

MA.3.GR.2.2

Find the area of a rectangle with whole-number side lengths using a visual model and a multiplication formula.

Key Point: Students connect counting squares to multiplication: Area = length × width. Visual models should accompany formula use.

MA.3.GR.2.3

Solve mathematical and real-world problems involving the perimeter of polygons with whole-number side lengths.

Key Point: Perimeter = distance around. Students add all side lengths. Includes rectangles and other polygons.

MA.3.GR.2.4

Solve mathematical and real-world problems involving the perimeter and area of composite figures composed of non-overlapping rectangles with whole-number side lengths.

Key Point: L-shapes, T-shapes made of rectangles. Decompose into smaller rectangles, find each area, then add.

Area	Perimeter
Space INSIDE a shape	Distance AROUND a shape
Measured in SQUARE units (sq cm, sq in)	Measured in LINEAR units (cm, in, ft)
Use multiplication: length × width	Use addition: add all sides
Think: "How much carpet to cover the floor?"	Think: "How much fence to go around the yard?"

Common Misconceptions & Fixes

Misconception: Confusing area and perimeter

Students mix up which concept uses multiplication vs. addition, or confuse square units with linear units.

Fix: Use consistent language: "Area = INSIDE, Perimeter = AROUND." Have students touch the inside (area) then walk around (perimeter) actual rectangles. Always label units correctly.

Misconception: Only counting visible sides for perimeter

In composite figures, students forget to count sides that aren't drawn on the outer edge.

Fix: Have students trace their finger around the ENTIRE outside while counting. For L-shapes, mark each segment and count systematically.

Misconception: Thinking perimeter uses multiplication

Students see a rectangle and automatically multiply length × width regardless of whether the problem asks for area or perimeter.

Fix: Require students to identify the question first: "Am I finding INSIDE or AROUND?" Circle the key word in problems before solving.

Misconception: Counting grid lines instead of squares for area

Students count the lines on a grid instead of the unit squares inside.

Fix: Have students color or shade each square as they count. Emphasize: "We count SQUARES, not lines."

Misconception: Adding only two sides for perimeter

Students add length + width instead of adding all four sides (or using 2l + 2w).

Fix: Always label ALL sides before adding. For rectangles, remind: "Opposite sides are equal" so label all four.

5-Day Lesson Sequence

Day 1: Exploring Area with Unit Squares (MA.3.GR.2.1)

Provide 1-inch square tiles and various rectangle outlines
Have students cover each rectangle completely - no gaps, no overlaps
Count the squares to find area
Introduce "square units" - why we say "square inches" not just "inches"
Practice with rectangles on grid paper

Day 2: Area Formula (MA.3.GR.2.2)

Connect counting to multiplication: 4 rows of 5 = 4 × 5 = 20
Introduce Area = length × width
Practice with visual models (grid rectangles)
Move to rectangles with just dimensions labeled (no grid)
Emphasize: formula is a SHORTCUT for counting squares

Day 3: Perimeter of Rectangles and Polygons (MA.3.GR.2.3)

Walk around the classroom - that's the perimeter!
Use string to measure around shapes
Add all side lengths
For rectangles: opposite sides are equal, so add all 4
Practice with irregular polygons (triangles, pentagons)

Day 4: Composite Figures (MA.3.GR.2.4)

Introduce L-shapes and T-shapes made of rectangles
Strategy: Decompose into smaller rectangles
Find area of each part, then ADD together
For perimeter: trace around the OUTSIDE only
Practice with real-world examples (room layouts, gardens)

Day 5: Mixed Practice & Word Problems

Mix area and perimeter problems - students identify which to find
Real-world contexts: fencing, carpeting, painting, garden beds
Practice FAST-format questions
Include composite figure problems

Differentiation Strategies

For Struggling Learners

Use physical manipulatives (square tiles, string) throughout
Always provide grid paper for area problems
Color-code: blue for perimeter (around), green for area (inside)
Create anchor charts with real-world examples
Practice one concept at a time before mixing

For Advanced Learners

Find missing side lengths given area or perimeter
Create their own composite figures and find measurements
Design a room layout with specific area requirements
Explore: Can two rectangles have same perimeter but different areas?
Multi-step problems involving both area and perimeter

FAST Test Tip:

FAST often includes problems where students must find BOTH area and perimeter, or where they must distinguish between the two. Watch for problems with composite figures and real-world contexts like fencing (perimeter) vs. painting (area).

Teacher Guide: Area & Perimeter