What you have to understand about Google is it was originally conceived to rank webpages based on links to the webpage. More links flowing to a page, higher the page should be ranked.
In reality it’s not that simple, all webpages are not equal when it comes to passing on PR, but the basic premise holds, more links = better rankings. See image for a better idea how PR is distributed via links, PR flows though links and ‘accumulates’ on pages where more PageRank flows through.
Pages B and C gain more PR, but note Page C only has the one link from Page B, that’s because Page B only links to Page C passing on approximately 85% of it’s ‘accumulated’ PR.
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