In the centre of a circle 9ft. in radius is a frog. It begins to jump in straight lines to the circunference of the circle. It's first jump is 4ft 6 ins, it's second 2ft 3 ins and it continues to jump half the length of the preceding jump. How many jumps does the frog make to get out of the circle?

Yes I know not the most inspiring post, but it's Monday.