Missing side perimeter worksheets

Missing-side perimeter problems reverse the usual process. Instead of adding known side lengths to find the perimeter, students receive the total perimeter and enough information to determine an unknown length. The worksheet mixes rectangles and squares and keeps every dimension a positive whole number.

Each diagram identifies the missing side and displays the known perimeter. Students can reason with equal opposite sides, subtract the known contributions from the total and divide what remains when necessary. Select one shape type for a focused lesson or retain mixed practice, and choose centimeters, meters, inches or feet.

A step-by-step missing-side strategy

• Mark equal opposite sides on a rectangle before calculating.
• Add the side lengths that are already known, including repeated opposite sides.
• Subtract that known total from the full perimeter.
• Decide whether the remaining amount represents one side or two equal sides.
• Substitute the answer into the diagram and add around the shape to verify the perimeter.

Why the check matters

A missing length must rebuild the stated perimeter when all four sides are added. This substitution check exposes common mistakes such as subtracting only one copy of a known side or forgetting that a rectangle has two equal lengths and two equal widths. Encourage students to write the final verification beside each problem.

How to print this worksheet

1. Check the settings above. They are already set for missing side perimeter problems.
2. Pick 10, 15, 20 or 30 problems, a title, and the name or date lines you want.
3. Choose US Letter or A4 to match the paper in your printer.
4. Press Download PDF for a file you can save and reuse, or Print to send it straight to your printer.
5. Keep the answer key page for yourself. The sheet number in the footer lets you make the exact same sheet again later.