What is the formula and SI unit for the area of a circle?

The formula for the area of a circle is A = πr², where A represents the area, π is a constant approximately equal to 3.14159, and r is the radius of the circle. This formula is derived from the relationship between the radius and the area, showing that the area is proportional to the square of the radius.

The SI unit for area is square meters (m²), which is appropriate for expressing the area of a circle in a scientific context. This ensures consistency with other measurements in physics and engineering where the metric system is used.

Other options present incorrect formulas for calculating the area of a circle. For instance, some options reference the diameter or circumference instead of the radius, which would not yield the correct result for area calculation. Additionally, the units presented in those options might not align correctly, reinforcing that the area requires a measure of two dimensions, hence square units.