Area and Circumference of Circles

Front

What is the formula for the circumference of a circle?

Back

C = 2πr, where C is the circumference and r is the radius.

Front

How do you calculate the area of a circle?

Back

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

Front

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

Back

The area increases by a factor of four.

Front

What is the relationship between the diameter and the radius of a circle?

Back

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

Front

How do you convert diameter to radius?

Back

Radius is half of the diameter (r = d/2).

Front

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

Back

C = 2π(5) = 31.42 cm.

Front

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

Back

A = π(5)² = 78.54 square feet.

Front

What is the circumference of a circle with a diameter of 12 inches?

Back

C = π(12) = 37.68 inches.

Front

If a circle has a radius of 3 m, what is its area?

Back

A = π(3)² = 28.27 square meters.

Front

What is the formula for calculating sales tax?

Back

Sales Tax = Price × Tax Rate.