Circumference and Area of Circles

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd, where r is the radius and d is the diameter.

Front

What is the formula for the area of a circle?

Back

A = πr², where r is the radius.

Front

If the radius of a circle is 8 m, what is the circumference? (Round to the nearest tenth)

Back

50.3 m.

Front

What is the diameter of a circle if the radius is 5 cm?

Back

Diameter = 2 * radius = 10 cm.

Front

What is the diameter of a circle with a circumference of 31.4 m?

Back

Diameter = Circumference / π = 10 m.

Front

If the diameter of a circle is 12 in., what is the circumference? (Round to the nearest tenth)

Back

37.7 in.

Front

What is the area of a circle with a radius of 9 cm?

Back

A = π(9)² = 254.47 cm².

Front

What is the term for a line segment that connects the center of a circle to any point on its circumference?

Back

Radius.

Front

What is the term for a line that goes from one end of the circle to the other and crosses the center point?

Back

Diameter.

Front

If the diameter of a pot is 18 cm, what is the area of the pot's bottom? (Round to the nearest whole number)

Back

254 cm².