Problem 4)
We want to know the value of r when the speed (V) is 55 mph. So we'll plug in V = 55 and solve for r.
\(V = \sqrt{2.5r}\)
\(55 = \sqrt{2.5r}\)
\((55)^2 = \left(\sqrt{2.5r}\right)^2\)
\(3025 = 2.5r\)
\(\frac{3025}{2.5} = \frac{2.5r}{2.5}\)
\(1210 = r\)
\(r = 1210\)
Therefore the radius of the curve is 1210 feet
