CCSS.Math.Content.3.MD.D
The standard
Geometric measurement: recognize perimeter as an attribute of plane figures and distinguish between linear and area measures.
Common Core State Standards for Mathematics
What this standard means
Students need to understand perimeter as the distance around a flat shape. They should measure or add side lengths to find it, and explain why perimeter uses length units like inches, feet, or centimeters.
Mastery looks like choosing perimeter when asked about fencing, borders, or distance around, and choosing area when asked about covering a surface. Students often mix up perimeter and area, count square units for perimeter, or forget to include all sides of a shape.
Ways to teach it
- Give pairs string and rulers to outline cardboard polygons, then measure the string to find each perimeter.
- Ask students to write which measure they need for a garden fence and which for grass seed, then explain why.
- Show a rectangle with labeled sides and ask students to find perimeter, area, and name the units for each.
- Have students measure the perimeter of their desk, math book, or a classroom rug and label the answer in length units.
Plan a lesson for CCSS.Math.Content.3.MD.D
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Related standards
- CCSS.Math.Content.4.MD.C
Geometric measurement: understand concepts of angle and measure angles.
- CCSS.Math.Content.3.MD.C
Geometric measurement: understand concepts of area and relate area to multiplication and to addition.
- CCSS.Math.Content.3.MD.C.5
Recognize area as an attribute of plane figures and understand concepts of area measurement.
- CCSS.Math.Content.4.G.A.2
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. ...