Diameter is a line segment that passes through the center of a circle with both its endpoints lying on the circle.
A diameter is the longest chord of a circle.
A diameter is double the radius of a circle.
In the circle shown, the line segments AB and PQ are the diameters of the circle. Notice that they have their endpoints on the circle and that both of them pass through the center O of the circle.

A. 64 cm
B. 32 cm
C. 16 cm
D. 8 cm
Correct Answer: C
Step 1: Diameter of a circle = 2 × radius.
Step 2: Therefore, radius =
.
Q1: A circle has a radius of 8 cm. What is its diameter?
Q2: The diameter of a circle is 32 cm. What is the radius?
Q: Is the diameter always twice the radius?
A: Yes, the diameter is always twice the length of the radius in any circle.
Q: Can a circle have more than one diameter?
A: Yes, a circle has infinitely many diameters.