Circle Area and Radius Concepts

The video tutorial explains how to find the area of a circle using the formula A = πr². It distinguishes between exact and approximate answers, emphasizing the use of the PI symbol for exact answers and 3.14 for approximations. The tutorial covers calculating the area using both radius and diameter, highlighting the need to convert diameter to radius. It also demonstrates working backwards from a given area to find the radius or diameter. The video concludes with a caution to carefully read questions to avoid common mistakes.

What is the formula for the area of a circle?

• Area = πd

• Area = πr²

• Area = 2πd

• Area = 2πr

Why is it important to use the radius in the area formula?

• The formula only works with the radius.

• The formula is more accurate with the radius.

• The diameter is too large.

• The radius is easier to measure.

How do you convert a diameter to a radius?

• Divide by 2

• Multiply by 2

• Add 2

• Subtract 2

What is the first step in calculating the area of a circle with a given radius?

• Square the radius

• Multiply the radius by 2

• Add π to the radius

• Multiply the radius by π

What is the exact area of a circle with a radius of 8 inches?

• 64π inches²

• 128π inches²

• 32π inches²

• 16π inches²

How do you find the approximate area of a circle?

• Use π as 3.14

• Use π as 3.14159

• Use π as 3.0

• Use π as 3.2

What is the radius of a circle with a diameter of 15 feet?

• 10 feet

• 30 feet

• 7.5 feet

• 15 feet

What is the exact area of a circle with a radius of 7.5 feet?

• 15π feet²

• 28.125π feet²

• 112.5π feet²

• 56.25π feet²

What is the approximate area of a circle with a radius of 7.5 feet?

• 200 feet²

• 100 feet²

• 150 feet²

• 176.63 feet²

What is the first step when working backwards from the area to find the radius?

• Subtract π from the area

• Add π to the area

• Divide the area by π

• Multiply the area by π