RADIUS
Definition Of Radius
Radius is the distance from the center of a circle or a sphere to any point on the circle or a sphere.
In other words, radius is a line segment joining the center of a circle with any point on the circle.
Examples of Radius
is a radius of the circle shown.
Video Examples: How to Find a Radius Between Two Points
Solved Example on Radius
Ques: Find the radius of a circle with area 153.86 square inches. Take π = 3.14
Choices:
A. 8
B. 7
C. 6
D. 5
Correct answer: B
Solution:
Step 1: Area of a circle of radius r = π r2 [Original equation.]
Step 2: 153.86 = 3.14 r2 [Substitute values.]
Step 3: 
[Divide each side by 3.14.]
Step 4: 49 = r2 [Simplify.]
Step 5: 
[ Evaluate square root on both sides.]
Step 6: r = 7 [Ignore the negative value.]
Quick Summary
- Radius is the distance from the center to any point on the circle.
- Radius is half the diameter of a circle.
- Radius is used in calculating circumference and area of a circle.
🍎 Teacher Insights
Use visual aids and real-world examples to illustrate the concept of radius. Emphasize the relationship between radius, diameter, circumference, and area. Provide ample practice problems.🎓 Prerequisites
- Circles
- Center of a Circle
- Distance
Check Your Knowledge
Q1: What is the radius of a circle with area 153.86 square inches (π = 3.14)?
Q2: The diameter of a circle is 10 cm. What is the radius?
Frequently Asked Questions
Q: What is the relationship between radius and diameter?
A: The diameter of a circle is twice its radius.
Q: How do you find the radius if you know the area of a circle?
A: Divide the area by pi and then take the square root.