GED Mathematical Reasoning TestQuantitative Problem Solving with MeasurementMedium
A circular swimming pool has a diameter of 20 feet. What is the approximate circumference of the pool? (Use π ≈ 3.14)
- A31.4 feet
- B62.8 feet
- C125.6 feet
- D314 feet
Show answer & explanationAnswer & explanation
Correct answer: B. 62.8 feet
The circumference of a circle is calculated using the formula C = πd, where d is the diameter. Given a diameter of 20 feet and π ≈ 3.14, the circumference is 3.14 * 20 = 62.8 feet.
Why the other options are wrong
- A. This would be the circumference if the radius was 10 feet (C = 2πr = 2 * 3.14 * 10 = 62.8), but the question asks for circumference using diameter.
- C. This is double the correct circumference.
- D. This is the area if the radius was 10 feet (A = πr²) or circumference if diameter was 100 feet.
Circumference of a Circle
The distance around the edge of a circle.
- Calculated using the formula C = πd or C = 2πr.
- π (pi) is a mathematical constant approximately equal to 3.14159.
- Units are linear (e.g., feet, meters).
Memory trick: Circles are round, so they have circumference, not perimeter.