Understanding the Area of a Circle

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

• A = 2πr

• A = πr²

• A = πd

• A = 2πd

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

• 50 square decimeters

• 25 square decimeters

• 100 square decimeters

• 78.5 square decimeters

How do you calculate the area of a circle with a radius of 9 inches?

• A = 3.14 × 81

• A = 3.14 × 9

• A = 3.14 × 45

• A = 3.14 × 18

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

• Diameter is half the radius

• Diameter is twice the radius

• Diameter is equal to the radius

• Diameter is three times the radius

If a circle's diameter is 12 inches, what is the area?

• 113.04 square inches

• 36 square inches

• 72 square inches

• 144 square inches

What formula should be used if the diameter is given?

• A = π × d²

• A = π × d

• A = π × (d/2)²

• A = 2π × d

What is the approximate value of π used in these calculations?

• 3.75

• 3.50

• 3.14

• 3.00

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

• 200 square inches

• 100 square inches

• 49 square inches

• 153.86 square inches

Which of the following is NOT a correct formula for the area of a circle?

• A = π × (d/2)²

• A = π × r × r

• A = πr²

• A = 2πr

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

• 31.4 square inches

• 50 square inches

• 78.5 square inches

• 100 square inches