Whenever you mention a benefit that is connected with the deen for e.g. if you say you are promised such and such benefit or garunteed such and such if you recite this or that (from the Quran or Sunnah) then for such a thing you need to have a evidence from Allah or his messenger, nobody noes the ilmul ghayb (knowledge of the unseen) so who gave you the authority to say reading ar rahman a 100 times will increase your memory? you cannot prove it sciencetifically so you need to prove it from the deen, nor i or any scholar i can refer to can give evidence or prove to this, We should always speak with proper knowledge because this is a fundamental principle in Islam. Imam Bukhari put a chapter in his sahih (book of hadith) titled "knowledge before speech and action" and the proof for this priciple in the Quran is where Allah says in Surah Muhammad Verse 19 "So have Knowledge that there is none that is worthy of worship except Allah..."