Area of Crircles

Front

What is the formula for the area of a circle?

Back

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

Front

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

Back

A = π(5 cm)² = 25π cm² ≈ 78.5 cm².

Front

What does π (pi) represent in the context of circles?

Back

π (pi) is a mathematical constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

How do you find the radius if you know the area of the circle?

Back

To find the radius, rearrange the area formula: r = √(A/π).

Front

What is the area of a circle with a diameter of 10 inches?

Back

First, find the radius: r = diameter/2 = 5 inches. Then, A = π(5 inches)² = 25π inches² ≈ 78.5 inches².

Front

What is the area of a circle with a radius of 3 m?

Back

A = π(3 m)² = 9π m² ≈ 28.3 m².

Front

If the area of a circle is 50.3 cm², what is the radius?

Back

Using the formula r = √(A/π), r = √(50.3/π) ≈ 4.0 cm.

Front

What is the relationship between the radius and diameter of a circle?

Back

The diameter is twice the radius: diameter = 2 × radius.

Front

How does changing the radius affect the area of a circle?

Back

The area increases with the square of the radius; if the radius doubles, the area increases by a factor of four.

Front

What is the area of a circle with a radius of 7.1 km?

Back

A = π(7.1 km)² ≈ 158.1 km².