Virginia SOL 3.MG.2.b.iii
The Standard
given the lengths of all sides of a polygon (with no more than six sides), determine its perimeter and justify the measurement.
Virginia Standards of Learning for Mathematics · The student will use multiple representations to estimate and solve problems, including those in context, involving area and perimeter (in both U.S. Customary and metric units).
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students add the labeled lengths of every side of a polygon with up to six sides. They show an addition equation and report the total in linear units.
What Mastery Looks Like
- A student traces the boundary and includes each side exactly once. They add accurately, name the correct unit, and explain that perimeter measures the distance around the polygon.
Common Misconceptions
- Students may skip a side or count one side twice. They may multiply length by width, assume unlabeled sides are equal, or write square units instead of linear units.
How to Assess It
- Give students an irregular pentagon labeled 2 cm, 3 cm, 4 cm, 5 cm, and 6 cm. Ask for its perimeter, an equation, and a sentence explaining their method.
Lesson moves
Ways to Teach It
Give pairs six cut straws with labeled lengths; have them build a closed polygon, then add the lengths and label its perimeter.
Write and discuss: Why must every outer side be included when finding the distance around a polygon?
Play Perimeter Match: students pair polygon cards with equation cards and total cards, then explain one match to a partner.
Show a labeled plan of a five-sided garden; students calculate the fencing needed and explain why no square units appear.
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Printable 3.MG.2.b.iii Worksheet
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- 3.MG.2.b.ii
estimate and measure the distance around a polygon (with no more than six sides) to determine the perimeter and justify the measurement; and
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