Problem of the Week due by Friday (optional)

Gordon Greenthumbs grows huge plants.  He grew zucchini that started out 6 inches and then grew 9 inches more overnight into the second day.  Each night the zucchini grew by the same amount as it grew the night before, plus another 3 inches.  On which day would the zucchini be LONGER than 11 feet?  Show work!