Grade 3 Geometry: Area and Perimeter

Worked examples

Real problems from the practice worksheets, solved one step at a time.

1. Example 1

   A rectangle has an area of 14 square feet. Its length is 7 ft. What is its perimeter in feet?

   1. Area = length × width, so the width is 14 ÷ 7 = 2 ft.
   2. Perimeter = 2 × (length + width) = 2 × (7 + 2) = 18 feet.

   Answer: 18

2. Example 2

   Rectangle A is 1 cm by 10 cm. Rectangle B is 2 cm by 9 cm. They have the same perimeter. How many more square centimeters of area does Rectangle B have?

   1. Area of Rectangle A = 1 × 10 = 10 square centimeters.
   2. Area of Rectangle B = 2 × 9 = 18 square centimeters.
   3. Rectangle B has 18 − 10 = 8 square centimeters more.

   Answer: 8

3. Example 3

   A rectangular playground is 6 m long and 4 m wide. How many meters long is a path all the way around its edge?

   1. Perimeter is the distance all the way around the rectangle. Add the four sides.
   2. Perimeter = 6 + 4 + 6 + 4 = 2 × (6 + 4) = 20 meters.

   Answer: 20