Real-World Examples of Radius and Diameter in Everyday Life

📚 Quick Study Guide

• 📏 Radius: The distance from the center of a circle to any point on its edge. It's half the diameter.
• 📐 Diameter: The distance across a circle through the center. It's twice the radius.
• ➗ Formula for Radius: $r = \frac{d}{2}$, where $r$ is the radius and $d$ is the diameter.
• ✖️ Formula for Diameter: $d = 2r$, where $d$ is the diameter and $r$ is the radius.
• ⏱️ Key Relationship: Understanding that the diameter is always twice the radius (and vice versa) is crucial.

🧪 Practice Quiz

1. What part of a bicycle wheel represents its radius?
   1. The entire wheel.
   2. The spoke from the center to the rim.
   3. The tire.
   4. The axle.
2. A circular pizza has a diameter of 16 inches. What is its radius?
   1. 4 inches
   2. 8 inches
   3. 16 inches
   4. 32 inches
3. Which of the following objects typically uses the concept of radius in its design?
   1. A square table
   2. A rectangular book
   3. A round clock
   4. A triangular sign
4. The distance around a circular garden is 50 feet. A gardener wants to place a sprinkler in the exact center. What measurement is most important to determine the sprinkler's spray coverage?
   1. The garden's area
   2. The garden's diameter
   3. The garden's radius
   4. The garden's perimeter
5. A circular swimming pool has a radius of 10 meters. What is the diameter of the pool?
   1. 5 meters
   2. 10 meters
   3. 20 meters
   4. 100 meters
6. A manufacturer is designing a circular lens for a camera. If the lens needs to be 4 cm across at its widest point, what radius should they use?
   1. 1 cm
   2. 2 cm
   3. 4 cm
   4. 8 cm
7. Which of these is the best real-world example of a diameter?
   1. The length of a straight path across a circular park, passing through its center.
   2. The distance from the center of a dartboard to the bullseye.
   3. The height of a building.
   4. The width of a rectangular window.