Area and Circumference

Front

What is the formula for the circumference of a circle?

Back

Circumference = π × diameter or Circumference = 2 × π × radius.

Front

What is the value of π (pi) approximately?

Back

π is approximately 3.14.

Front

If the diameter of a circle is 14 cm, what is the radius?

Back

The radius is half of the diameter, so the radius is 7 cm.

Front

How do you calculate the area of a circle?

Back

Area = π × radius².

Front

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

Back

Area = π × (3 in)² = 28.26 in².

Front

What is the circumference of a circle with a radius of 10 cm?

Back

Circumference = 2 × π × 10 cm = 62.8 cm.

Front

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

Back

Diameter = Circumference / π = 31.4 in / 3.14 = 10 in.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the radius (Diameter = 2 × Radius).

Front

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

Back

The area increases by a factor of four (Area = π × (2r)² = 4 × π × r²).

Front

What is the circumference of a circle with a diameter of 20 cm?

Back

Circumference = π × 20 cm = 62.8 cm.