If I know something with 51% certainty of being true, how many other independant facts on the same subject (all with 51% certainty of being true) do I need to know to have 99% certainty that my knowlege of the subject is correct? 

This is assuming that any one 51% probability fact being proven false would disprove all my knowledge on the subject.

This came up in a discussion on science, where I asserted that no piece of knowledge has to be 99% certain to be 99% certain overall, because when we aggregate independant but related facts, the probability of being correct is greater than the probability of any one fact being correct.