Area and circumference of circles

Front

What is the formula for the circumference of a circle?

Back

The formula for the circumference of a circle is C = 2πr, where r is the radius.

Front

What is the definition of the radius of a circle?

Back

The radius of a circle is the distance from the center of the circle to any point on its edge.

Front

What is the formula for the area of a circle?

Back

The formula for the area of a circle is A = πr², where r is the radius.

Front

How do you calculate the radius from the diameter of a circle?

Back

The radius is half of the diameter. If the diameter is d, then r = d/2.

Front

How do you calculate the diameter from the radius of a circle?

Back

The diameter is twice the radius. If the radius is r, then d = 2r.

Front

What is the value of π (pi) approximately?

Back

The value of π (pi) is approximately 3.14.

Front

If the radius of a circle is 5 cm, what is the circumference?

Back

The circumference is C = 2πr = 2 × 3.14 × 5 = 31.4 cm.

Front

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

Back

The area is A = πr² = 3.14 × 7² = 153.86 m².

Front

What is the relationship between radius and diameter?

Back

The diameter is always twice the radius.

Front

If a circle has a circumference of 31.4 cm, what is its radius?

Back

Using the formula C = 2πr, the radius r = C/(2π) = 31.4/(2 × 3.14) = 5 cm.