Understanding the Area of a Circle

The video tutorial reviews the formulas for calculating the circumference and area of a circle. It explains the formulas for circumference as C = πd and C = 2πr, and the area as A = πr². The tutorial provides examples of calculating the area using a given radius, converting diameter to radius, and finding the area of a semicircle. It emphasizes the importance of distinguishing between radius and diameter when solving problems.

What is the formula for the circumference of a circle using the diameter?

• C = πd

• C = 2πr

• C = 2πd

• C = πr²

If the radius of a circle is 6 cm, what is the area of the circle?

• 113.04 cm²

• 36 cm²

• 226.08 cm²

• 113.40 cm²

How do you find the radius if you are given the diameter of a circle?

• Add 2 to the diameter

• Multiply the diameter by 2

• Square the diameter

• Divide the diameter by 2

Given a diameter of 16 feet, what is the area of the circle?

• 200.96 ft²

• 256 ft²

• 804.24 ft²

• 201.06 ft²

What additional step is needed when calculating the area of a semicircle?

• Subtract π from the area

• Add π to the area

• Multiply the area by 2

• Divide the area by 2

If the radius of a semicircle is 3.6 meters, what is the area of the semicircle?

• 81.38 m²

• 10.18 m²

• 20.35 m²

• 40.69 m²

What is the formula for the area of a circle?

• A = 2πd

• A = πr²

• A = 2πr

• A = πd

Why is it important to know whether you have the radius or diameter when calculating the area?

• The diameter is needed for the area formula

• The radius is needed for the area formula

• The circumference is calculated differently

• The formula changes based on the diameter

What is the value of π used in these calculations?

• 3.41

• 3.04

• 3.14

• 3.00

Which of the following is NOT a formula for circumference?

• C = 2πd

• C = πd

• C = 2πr

• C = πr²