If a circle's diameter is d, which statement is true about the radius?

If a circle's diameter is d, which statement is true about the radius?

• A. Radius equals d/2
• B. Radius equals d
• C. Radius equals 2d
• D. Radius equals sqrt(d)

Answer: (A)

Radius is half of the diameter. The radius is the distance from the center to any point on the circle, while the diameter stretches across the circle through the center and is made up of two radii end to end. That means the diameter’s length is twice the radius. So, if the diameter is d, the radius must be d/2. For a quick check, double the radius to get the diameter, or halve the diameter to get the radius; for example, a diameter of 10 gives a radius of 5.

Radius is half of the diameter. The radius is the distance from the center to any point on the circle, while the diameter stretches across the circle through the center and is made up of two radii end to end. That means the diameter’s length is twice the radius. So, if the diameter is d, the radius must be d/2. For a quick check, double the radius to get the diameter, or halve the diameter to get the radius; for example, a diameter of 10 gives a radius of 5.