2019 AMC 12A Problem 1

The areas are proportional to the squares of the radii, so the ratio of the larger area to the smaller is $\dfrac{16}{9}.$ The percent increase is $$\left(\dfrac{16}{9} - 1\right) \times 100 = \dfrac{700}{9} \approx 77.8.$$ The closest integer is $78.$ Thus, the correct answer is E.