Circles - Area and Circumference

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr or Circumference = πd, where d is the diameter.

Front

If the diameter of a circle is 10 cm, what is the radius?

Back

Radius = Diameter / 2 = 10 cm / 2 = 5 cm.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

How do you convert circumference to radius?

Back

Radius = Circumference / (2π).

Front

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

Back

Area = π(7)² ≈ 153.94 cm².

Front

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

Back

Diameter = Circumference / π = 31.4 cm / π ≈ 10 cm.

Front

What is the value of π (pi) approximately?

Back

π ≈ 3.14.

Front

What is the area of a circle with a diameter of 8 cm?

Back

Area = π(4)² ≈ 50.27 cm².

Front

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

Back

The area increases by a factor of 4.