In 1987, a New York State Assembly woman wrote a letter to her constituents about the electric rates of the Long Island Lighting Company. She wrote: "If the public service commission grants this increase, it will mean that between 1970 and 1987, the electric rates will have increased by more than 478 percent. That's an average rise of over 27 percent a year!" Is this correct? If not, what annual percent increase of 17 years leads to a total increase of 478 percent?

Question

In 1987, a New York State Assembly woman wrote a letter to her constituents about the electric rates of the Long Island Lighting Company.  She wrote: "If the public service commission grants this increase, it will mean that between 1970 and 1987, the electric rates will have increased by more than 478 percent.  That's an average rise of over 27 percent a year!"  Is this correct?  If not, what annual percent increase of 17 years leads to a total increase of 478 percent?