Circumference and Area

Front

What is the formula for the area of a circle?

Back

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

Front

What is the formula for the circumference of a circle?

Back

The circumference C of a circle is given by the formula C = 2πr or C = πd, where r is the radius and d is the diameter.

Front

If a circle has a radius of 5, what is its area?

Back

The area is A = π(5)² = 25π or approximately 78.54.

Front

If a circle has a diameter of 10, what is its circumference?

Back

The circumference is C = πd = π(10) = 10π or approximately 31.42.

Front

What is the relationship between radius and diameter?

Back

The diameter d of a circle is twice the radius r, so d = 2r.

Front

How do you convert diameter to radius?

Back

To convert diameter to radius, divide the diameter by 2: r = d/2.

Front

What is the area of a circle with a radius of 3?

Back

The area is A = π(3)² = 9π or approximately 28.27.

Front

What is the circumference of a circle with a radius of 7?

Back

The circumference is C = 2π(7) = 14π or approximately 43.98.

Front

What is the value of π (pi) approximately?

Back

The value of π is approximately 3.14.

Front

If the circumference of a circle is 31.4, what is the radius?

Back

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