Calculate radius, diameter, and circumference (Advanced)

Learning Objectives Accurately calculate the circumference of a circle given its radius or diameter. Accurately calculate the radius or diameter of a circle given its circumference. Apply appropriate approximations for pi (e.g., 3.14 or 22/7) based on problem context. Express circumference, radius, or diameter in terms of pi for exact answers. Solve multi-step word problems involving radius, diameter, and circumference. Identify and correct common errors in calculating circle measurements. Ever wondered how much fencing you'd need for a circular garden, or how far a bicycle wheel travels in one rotation? 🚴‍♀️ These questions all involve understanding circles! In this lesson, we'll dive deeper into calculating the radius, diameter, and circumference of circles. Yo...

TermDefinitionExample CircleA set of all points in a plane that are equidistant from a fixed point called the center.A hula hoop or the edge of a coin are examples of circles. Radius (r)The distance from the center of a circle to any point on its edge. It's half the diameter.If a pizza has a diameter of 14 inches, its radius is 7 inches. Diameter (d)The distance across a circle passing through its center. It's twice the radius.If a circular clock face has a radius of 6 inches, its diameter is 12 inches. Circumference (C)The distance around the outside of a circle. It's similar to the perimeter of a polygon.The length of the ribbon needed to go around a circular gift box is its circumference. Pi (π)A mathematical constant representing the ratio of a circle's circumferen...

Diameter from Radius $$d = 2r$$ To find the diameter of a circle, multiply its radius by 2. This rule also implies that $r = d/2$. Circumference from Diameter $$C = \pi d$$ To find the circumference of a circle, multiply its diameter by the constant pi (π). This is useful when the diameter is known. Circumference from Radius $$C = 2\pi r$$ To find the circumference of a circle, multiply 2 by pi (π) and then by the radius. This is useful when the radius is known.