GED Mathematical Reasoning TestQuantitative Problem Solving with MeasurementMedium
A city planner is designing a new public park that includes a circular plaza. The plaza will have a radius of 15 meters. If the city wants to install decorative lighting around the entire edge of the plaza, what is the total length of lighting needed, rounded to the nearest meter?
- A141 meters
- B94 meters
- C236 meters
- D47 meters
Show answer & explanationAnswer & explanation
Correct answer: B. 94 meters
The length of lighting needed is the circumference of the circular plaza. The formula for circumference is C = 2πr. Given a radius (r) of 15 meters, C = 2 * π * 15 ≈ 2 * 3.14159 * 15 ≈ 94.2477 meters. Rounded to the nearest meter, this is 94 meters.
Why the other options are wrong
- A. This would be the result if the radius was squared (πr²) which is the area, not circumference, or if 3πr was used.
- C. This would be the result if the diameter was squared (πd²) which is the area, or a significant calculation error.
- D. This would be the result if the diameter was used as the radius (2πd instead of 2πr) or a calculation error.
Circumference of a Circle
The circumference of a circle is the total distance around its outer edge.
- Formula: C = 2πr or C = πd, where r is radius and d is diameter.
- π (pi) is approximately 3.14159.
- Measured in linear units (e.g., meters, feet).
Memory trick: Two Pi R, for the circle's grand contour!