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3rd Grade Area & Perimeter Worksheets

Our 3rd grade area and perimeter worksheets provide comprehensive practice with 12 different worksheet types covering essential geometry skills. Students will find area using blocks and tiling, calculate perimeter, work with rectangles and rectilinear shapes, and solve missing side problems.

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Finding Length of a Side

About these worksheets

Students practice finding a missing side length of a rectangle or right triangle when given the area or perimeter. These worksheets reinforce the relationship between side lengths, area, and perimeter through reverse calculation — dividing area by a known side or subtracting known sides from a total perimeter. Problem sets span third grade through middle school, with some including decimal values.

3rd Grade Area & Perimeter Worksheets - Missing Side (Area) E worksheet

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Missing Side (Area) E

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Use the area of a rectangle to figure out a missing side length.
Divide the area by the known side to find the unknown side.
Check that the side lengths you found make the correct area when multiplied.

3rd Grade Area & Perimeter Worksheets - Missing Side (Perimeter) E worksheet