Since the area of any thing is length time width, we can divide 4864 by 152 to get the width of the garden. This gives us 32. Now we need to add 152 + 152 + 32 + 32 to get our total feet of fencing necessary. This would give us 368 feet of fencing.
Hmmm... a geometric sequence MUST have a fixed common ratio. If it is changing, then the sequence you are looking at might not be a geometric sequence at all. We'd need to see an example to be sure.