The formulas 10 = 2πr and A = πr^2 are proportional because the radius (r) in both formulas is directly related to the values on the other side of the equation. When the radius changes, the values on the other side of the equation change in a directly proportional manner. This is because the area of a circle is dependent on the radius, so as the radius increases or decreases, the area of the circle will also increase or decrease in a proportional manner.
