11.2 Areas of Circles & Sectors

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

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

Back

Use the formula r = √(A/π).

Front

What is a sector of a circle?

Back

A sector is a portion of a circle enclosed by two radii and the arc between them.

Front

How do you calculate the area of a sector?

Back

Area of sector = (θ/360) × πr², where θ is the angle in degrees.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

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

Back

Radius = 10 cm / 2 = 5 cm.

Front

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

Back

A = π(7)² ≈ 153.94 cm².

Front

How do you convert area from square inches to square feet?

Back

Divide the area in square inches by 144 (since 1 ft² = 144 in²).

Front

What is the area of a circle with a radius of 4 m?

Back

A = π(4)² ≈ 50.27 m².

Front

If a circle has an area of 78.54 cm², what is its radius?

Back

Radius = √(78.54/π) ≈ 5 cm.