Grade 7 Geometry: Circumference

Worked examples

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

1. Example 1

   A circle has a diameter of 22 inches. What is its circumference, in inches? Use 3.14 for π.

   1. The circumference of a circle is C = πd = 2πr.
   2. C = 3.14 × 22 = 69.08 inches.

   Answer: 69.08

2. Example 2

   A circle has a radius of 11 inches. What is its circumference, in inches? Use 3.14 for π.

   1. The circumference of a circle is C = πd = 2πr.
   2. The diameter is twice the radius: d = 2 × 11 = 22.
   3. C = 3.14 × 22 = 69.08 inches.

   Answer: 69.08

3. Example 3

   A circle has a circumference of 56.52 inches. What is its diameter, in inches? Use 3.14 for π.

   1. Start from C = πd, so d = C ÷ π.
   2. d = 56.52 ÷ 3.14 = 18.

   Answer: 18