Area and Circumference

Front

What is the formula for the area of a circle?

Back

The area (A) of a circle is calculated using the formula A = πr², where r is the radius of the circle.

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) of a circle is calculated using the formula C = 2πr, where r is the radius of the circle.

Front

What is the value of π (pi) to two decimal places?

Back

The value of π (pi) is approximately 3.14.

Front

If the radius of a circle is doubled, how does the area change?

Back

If the radius is doubled, the area increases by a factor of four, since area is proportional to the square of the radius.

Front

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

Back

The radius is half of the diameter, so the radius is 5 inches.

Front

What is the relationship between diameter and circumference?

Back

The circumference of a circle is directly proportional to its diameter, expressed as C = πd, where d is the diameter.

Front

How do you convert the circumference of a circle to its radius?

Back

To find the radius from the circumference, use the formula r = C / (2π).

Front

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

Back

The area is A = π(7)² = 49π, which is approximately 153.94 square inches.

Front

What is the circumference of a circle with a radius of 4 meters?

Back

The circumference is C = 2π(4) = 8π, which is approximately 25.13 meters.

Front

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

Back

First, find the radius (5 cm), then use the area formula: A = π(5)² = 25π, which is approximately 78.54 cm².