Circles - Area and Circumference

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd, where C is the circumference, r is the radius, and d is the diameter.

Front

What is the radius of a circle?

Back

The radius is a line segment from the center of the circle to any point on its circumference.

Front

What is the diameter of a circle?

Back

The diameter is a line segment that passes through the center of the circle and connects two points on its circumference. It is twice the length of the radius.

Front

If the radius of a circle is 7 cm, what is the area?

Back

A = π(7)² = 49π cm² (approximately 153.94 cm²).

Front

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

Back

Radius = diameter/2 = 20 cm / 2 = 10 cm.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the radius (d = 2r).

Front

What is the circumference of a circle with a radius of 5 cm?

Back

C = 2π(5) = 10π cm (approximately 31.42 cm).

Front

What does π (pi) represent in circle calculations?

Back

π is a constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

How do you convert diameter to circumference?

Back

Use the formula C = πd.