Circles Area and Circumference

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is the formula for the circumference of a circle?

Back

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

Front

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

Back

A = π(5)² = 25π ≈ 78.54 cm².

Front

If the diameter of a circle is 10 cm, what is its circumference?

Back

C = πd = π(10) ≈ 31.42 cm.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the radius: d = 2r.

Front

What is the area of a semicircle with a radius of 4 cm?

Back

A = (1/2)π(4)² = 8π ≈ 25.13 cm².

Front

How do you convert circumference to diameter?

Back

Use the formula d = C/π.

Front

What is the area of a circle with a radius of 7 cm?

Back

A = π(7)² = 49π ≈ 153.94 cm².

Front

If a circle has a circumference of 31.4 cm, what is its radius?

Back

r = C/(2π) = 31.4/(2π) ≈ 5 cm.

Front

What is the area of a circle with a diameter of 12 cm?

Back

A = π(6)² = 36π ≈ 113.10 cm².