Well, the number of articles doesn't have much to do with it.
What really makes the money with Adsense is when someone clicks an adsense ad, but you must be very very careful when discussing that. You most certainly can't click your own ads, or encourage anyone to click them either.
In fact, never even talk about adsense and clicks on your hubs or social networks - you shouldn't talk about that just to be safe. You can discuss some things, but some things are explicitly forbidden to talk about.
Basically, you have to write an outstanding article about anything you choose to write about first and foremost...but then if the topic you write about is heavily covered on the web, then you must realize that you've got a lot of competition going.
Some topics will bring high paying Adsense ads, and most often those topics are the ones with the most competition.
Were I to play the Adsense and Keyword game myself, then I would target keywords that are medium to low paying with Adsense, and have low competition.
I don't do any of that though, I just write what I want and hope for the best....sort of like a member of the band on the Titanic....