3rd grade decomposing rectilinear figures worksheets

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Decomposing rectilinear figures worksheets for 3rd grade print 6 problems per page. Use the dashed line to find the two rectangle areas. Then find the total area. Include square units. Split the shape into non-overlapping rectangles. Add their areas.

Free printable PDF worksheet, aligned to Common Core 3.MD.C.7.d.

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of problems you'll get

Use the dashed line to find the two rectangle areas. Then find the total area. Include square units.

  1. Two rectangles have areas of 6 and 4 square units. Find their combined area.

    Answer: 10 square units.

Most problems on this sheet sit beside a picture, model or diagram, so this is the worked example the sheet itself prints. The answer key on page two prints the answer under every problem.

Every print pulls a fresh set of problems at this level, so a make-up test or a second sibling never gets the same sheet.

What's on each sheet

Every version prints on US Letter or A4, with its answer key after the problems.

This sheet is one of the versions on the 3rd grade rectilinear area page, with its own difficulty choices and its own answer key.

How to teach this

Have your child draw one straight line that cuts the L into two rectangles before touching any numbers, then write a separate multiplication for each piece. If subtracting feels more natural, sketch the missing corner back in with a dotted line and take it away from the big rectangle. On the first figure, try both strategies. Matching answers is the best confidence builder there is.

Watch for: Kids multiply the two biggest labels and stop. The notch has to come off, or split the shape into two rectangles and add the parts. Kids add up all six side labels. That's the perimeter recipe, and area needs multiplying.

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Aligned to Common Core 3.MD.C.7.d. Reviewed by the One more sheet team. Content version 241, updated September 2026.

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