Circumference and Area of Circles

Front

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

Back

The circumference (C) of a circle can be calculated using the formula C = πd, where d is the diameter, or C = 2πr, where r is the radius.

Front

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

Back

The value of π (pi) to two decimal places is approximately 3.14.

Front

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

Back

The radius (r) of a circle is half of the diameter (d). Therefore, if the diameter is 10 cm, the radius is 5 cm.

Front

How do you convert diameter to radius?

Back

To convert diameter to radius, divide the diameter by 2.

Front

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

Back

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

Front

If a circle has a radius of 7 m, what is its area?

Back

Using the formula A = πr², the area is A = π(7)² = 49π ≈ 153.94 m².

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.

Front

How do you find the circumference if you only have the radius?

Back

If you have the radius (r), you can find the circumference using the formula C = 2πr.

Front

What is the circumference of a circle with a radius of 3 inches?

Back

Using the formula C = 2πr, the circumference is C = 2π(3) ≈ 18.85 inches.

Front

What is the diameter of a circle with a circumference of 31.4 cm?

Back

To find the diameter from the circumference, use the formula d = C/π. Therefore, d = 31.4/π ≈ 10 cm.