I'm admittedly still learning more about the stock market, but even I wasn't this bad at math....
"So, let us say you take that $200 right now and invest it in a mutual fund. 10% later in a month you will have $240. The next month, $264. The third month, $290. Fourth month, $319.44. So you understand this concept of compound interest, right?
Check the math I hope I made a big mistake because that is a lot of money. "
As people have already pointed out, 200 -> 240 is 20%, not 10%, and furthermore, investment gains tend to be counted at an ANNUAL rate. If there was a stock that gained 10% monthly, it would grow quite alot by the end of the year. Very few company stocks have made a large gain every year for a long period of time; Berkshire's an interesting exception in part because it's an equity company and deploys its float or reserves to acquire companies (to my understanding). Shame on you for not checking the math, since, again, as people have pointed out, there's a HUGE difference between 10% compounded monthly and 10% compounded annually (I believe a poster said $200 with 10% annual rate = ~8-9k after 40 years).
"Buy Apple and Cingular stock, SOON, and see where it is in a year. Or better yet wait until Steve Jobs shits hit pants and everyone sells their stock for a day and buy then and watch it recover 5% the next day."
The OP apparently wrote this July 9th. Apple's stock ended that day was 174.25, and AT&T (which owned Cingular) was at 32.12. Since then both stocks have slipped in value...in Oct and Nov apple has gone no higher than 111, and as of Friday's closing was 98.27. AT&T has gone no higher than 29.98 (a few days ago) and dropped to 28.18. So far both stocks have DECLINED in value since July, Apple about 44% since July 9th, and AT&T declined by about 13%.
Granted it's only been 5 months so far, but seeing as how neither stock has gained in value between now and early July, it might be safe to say that it's far from guaranteed that either stock will make your 10% prediction for the time being....