Hi Lexi,
I believe there is not enough information to answer this question! Is this the full question? Did you leave some out?
The problem tells us the baseball is 6cm. We also know there is a tightly wound string inside. I would say there is 6cm of string, because the baseball is 6cm. But the string is “tightly wound” which means there could be more than 6cm. I don’t see how we would have to round either. This problem doesn’t give enough whole numbers much less decimals.
Sorry I couldn’t help, maybe someone else will understand this problem.