Area and Perimeter: Unknown Side
Find an unknown rectangle side from its area or perimeter in these printable 4th grade visual math problems.
Worksheet version 1 of 12. The answer key matches the current version.
Use the given area or perimeter and one side to find the unknown side, x or a.
1. Area = 12 square cm. Find x.
Answer: ____________________
2. Perimeter = 16 cm. Find a.
Answer: ____________________
3. Area = 15 square cm. Find x.
Answer: ____________________
4. Perimeter = 22 cm. Find a.
Answer: ____________________
5. Area = 16 square cm. Find x.
Answer: ____________________
6. Perimeter = 22 cm. Find a.
Answer: ____________________
About this worksheet
An unknown side can be found from area by dividing by the known side. For perimeter, subtract both known sides and divide the remaining distance between the two equal unknown sides.
Print a student sheet, then choose “Show answer key” to print the matching answers. Choose “New worksheet” for another version; the answer key always follows the version on screen.
Practice aligned to CCSS 4.MD.A.3.
More practice: area and perimeter worksheets and 4th grade math worksheets.