Circles - Area and Circumference

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd

Front

If the circumference of a circle is 62.8 inches, what is the radius?

Back

10 inches

Front

How do you find the radius of a circle?

Back

Radius = Diameter / 2 (r = d/2)

Front

What is the formula for the area of a circle?

Back

A = πr²

Front

If the radius of a circle is 5 inches, what is the area?

Back

A = π(5)² = 25π ≈ 78.54 square inches

Front

What is the diameter of a circle?

Back

The diameter is twice the radius (d = 2r).

Front

If the diameter of a circle is 14 inches, what is the radius?

Back

7 inches

Front

What is the area of a circle with a diameter of 8 cm?

Back

A = π(4)² = 16π ≈ 50.27 cm²

Front

What is the circumference of a circle with a radius of 3 cm?

Back

C = 2π(3) = 6π ≈ 18.85 cm

Front

If a circle has an area of 1134.11 cm², what is the radius?

Back

r = √(A/π) = √(1134.11/π) ≈ 19 cm