Area and Circumference of Circles

Front

What is the formula for the area of a circle?

Back

The area (A) of a circle is calculated using the formula: A = πr², where r is the radius of the circle.

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) of a circle is calculated using the formula: C = 2πr or C = πd, where r is the radius and d is the diameter.

Front

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

Back

A = π(5 cm)² = 25π cm² ≈ 78.54 cm².

Front

If a circle has a diameter of 10 inches, what is its radius?

Back

The radius is half of the diameter, so r = 10 inches / 2 = 5 inches.

Front

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

Back

A = π(7 m)² = 49π m² ≈ 153.94 m².

Front

How do you convert diameter to radius?

Back

To convert diameter to radius, divide the diameter by 2: r = d / 2.

Front

What is the area of a circle with a diameter of 14 inches?

Back

First, find the radius: r = 14 inches / 2 = 7 inches. Then, A = π(7 inches)² = 49π in² ≈ 153.94 in².

Front

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

Back

C = 2π(3 cm) = 6π cm ≈ 18.85 cm.

Front

If the area of a circle is 28.26 cm², what is the radius?

Back

Using A = πr², we can find r: r = √(28.26/π) ≈ 3 cm.

Front

What is the relationship between diameter and circumference?

Back

The circumference is directly proportional to the diameter: C = πd.