Circles Area and Circumference Review

Front

What is the formula for the circumference of a circle?

Back

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

Front

What is the formula for the area of a circle?

Back

A = πr², where r is the radius.

Front

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

Back

The radius is 5 inches.

Front

What is the approximate value of π (pi)?

Back

π is approximately 3.14.

Front

How do you calculate the circumference of a circle with a radius of 4 cm?

Back

C = 2πr = 2 × 3.14 × 4 = 25.12 cm.

Front

What is the area of a circle with a radius of 7 cm?

Back

A = πr² = 3.14 × 7² = 153.86 cm².

Front

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

Back

The area increases by a factor of four.

Front

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

Back

C = πd = 3.14 × 12 = 37.68 meters.

Front

How do you find the area of a semicircle?

Back

A = (1/2)πr².

Front

What is the difference in area between two circles with radii of 10 cm and 5 cm?

Back

Area difference = π(10²) - π(5²) = 100π - 25π = 75π cm².