Testinar Grade 3 math

Perimeter of Polygons

Students will solve perimeter problems for polygons, including problems with an unknown side length.

CH06-10 Geometry and Measurement

Directions Solve each problem. Show your reasoning on the page or on separate paper. Check the answer key only after finishing.

A rectangle has length \(8\) cm and width \(5\) cm. What is its perimeter?
1. \(13\) cm
2. \(26\) cm
3. \(40\) cm
4. \(80\) cm
What is the perimeter of this rectangle in units?
1. \(9\) units
2. \(18\) units
3. \(36\) units
4. \(54\) units
This is a square with side length \(4\) m. What is its perimeter?
1. \(8\) m
2. \(12\) m
3. \(16\) m
4. \(24\) m
A rectangle has length \(10\) inches and width \(4\) inches. Find the perimeter.
1. \(28\) in
2. \(14\) in
3. \(40\) in
4. \(56\) in
What is the perimeter of this rectangle in centimeters?
1. \(7\) cm
2. \(14\) cm
3. \(10\) cm
4. \(28\) cm
A square has a perimeter of \(20\) feet. What is the length of one side?
1. \(5\) ft
2. \(4\) ft
3. \(10\) ft
4. \(20\) ft
What is the perimeter?
1. \(9\) units
2. \(18\) units
3. \(28\) units
4. \(35\) units
This is a square with side \(3\) inches. Find its perimeter.
1. \(9\) in
2. \(15\) in
3. \(12\) in
4. \(18\) in

Teacher and parent reference

Answer key and explanations

B. \(26\) cm
Perimeter \(=2\ell+2w=2(8)+2(5)=16+10=26\) cm.
B. \(18\) units
\(P = 2(6) + 2(3) = 12 + 6 = 18\) units.
C. \(16\) m
A square has 4 equal sides. \(P = 4 + 4 + 4 + 4 = 16\) m.
A. \(28\) in
\(P = 2(10) + 2(4) = 20 + 8 = 28\) in.
B. \(14\) cm
\(P = 2(5) + 2(2) = 10 + 4 = 14\) cm.
A. \(5\) ft
A square has 4 equal sides. \(20 \div 4 = 5\) ft per side.
B. \(18\) units
\(P = 2(7) + 2(2) = 14 + 4 = 18\) units.
C. \(12\) in
\(P = 4 \times 3 = 12\) in.