help!! redirecting old permalink structure to a new one

i recently changed my permalink structure from:

/%year%/%monthnum%/%day%/%postname%/

to

/articles/%category%/%postname%/

now the question is:

how do i redirect requests to the old permalinks to the new ones?

i’m asking because my blog has been fully indexed by google and most of my traffic is coming from google, so the new structure will result in broken links (404 pages) when people visit my blog from google’s search results.

and the reason i changed it is because i want to fill in more keywords there (better for seo in the long run).

any ideas?