Consider five circles with a radii of 1, 2, 4, 8, and 16 inches. Write your answer in terms of pi r square. Compare the areas and circumference of a circle when you double the radius? What happens to the area? What happens when you triple the radius. The table lists the radius, circumference and area.
When you change the radius (multiply by k), a 1D size, the circumference is multiplied by k (1D), while the area is multiplied by [latex]k^2[/latex] (2D). I hope this helps on this problem and others.