Worked examples
Two examples
Example 1
A circle has a radius of 5 cm. Use 3.14 for π. What is its circumference?
- C = 2πr = 2 × 3.14 × 5.
Answer: 31.4 cm
Example 2
A circle has a radius of 7 inches. What is its diameter?
- The diameter is twice the radius.
Answer: 14 inches
Where this is taught: Circles and Equations, “Unroll the edge”
The drill
Ten problems
This drill also has challenge problems. They use the same skill, set up the way the GED test sometimes sets up a problem, so that it looks new at first.
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.