I am a writer, i write content for the websites as well for the promotion of the web in search engine. When i get a question about the number of articles required to post in blogs for bringing a site in number one position i am not able to answer can you answer?

i think not so important
just naturally

It depends on the article you are writing and how much it is useful or having information related to you services and content must be unique , easy to under by the readers. Excess use of keyword in article is also not good . Lot more to take into consideration while writing an article .

Its depend upon you competors blogs or backlinks you need analysis any SEO expert can help you it is not possible for you to beign a writer you can put your keyword on first page

It depends on you and content of your article using for promotion.

You have to keep proper keyword density in mind...Before putting keywords in the content..

It is not justified answer. Since you are in seo writing, so you must be aware of fact that it is not the numbers of post. It is quality of posts and the platform importance where these are posted, that contribute in rank fixing.