Finding the Area of Circles

The video tutorial explains how to calculate the area of a circle using the formula A = πr². It covers the steps to find the radius from the diameter, substitute it into the formula, and solve for the area. Several examples are provided, demonstrating calculations with both given diameters and radii. The tutorial also explains how to express the area in terms of Pi for more precise results.

What is the formula for calculating the area of a circle?

• A = 2r^2

• A = 2πr

• A = πr^2

• A = πd

If the diameter of a circle is 20 units, what is the radius?

• 20 units

• 10 units

• 40 units

• 5 units

How do you calculate the area of a circle when given the radius?

• Double the radius and multiply by π

• Square the diameter and divide by 4π

• Square the radius and multiply by π

• Multiply the diameter by π

What is the area of a circle with a radius of 5 inches?

• 78.5 inches squared

• 157 inches squared

• 25 inches squared

• 314 inches squared

What is the area of a circle with a radius of 9 millimeters?

• 729 mm squared

• 81 mm squared

• 18 mm squared

• 254.34 mm squared

What is the area of a circle with a radius of 11 cm using the approximation of Pi as 3.14?

• 242 cm squared

• 121 cm squared

• 484 cm squared

• 379.94 cm squared

When expressing the area of a circle in terms of Pi, what is the formula used?

• A = πr

• A = πr^2

• A = 2πr

• A = r/π

If the diameter of a circle is 30 cm, what is the area in terms of Pi?

• 225π cm squared

• 900π cm squared

• 450π cm squared

• 15π cm squared

What is the radius of a circle if its diameter is 16 mm?

• 8 mm

• 32 mm

• 4 mm

• 16 mm

For a circle with a radius of 4.8 feet, what is the area in terms of Pi?

• 48π feet squared

• 19.2π feet squared

• 23.04π feet squared

• 9.6π feet squared