If you do the calculations it would actually be possible if you have a full room of bitcoin miners working all-together but in reality, most of us don't even own a mining rig, so in your question, it is not possible in that amount of time that you are asking with just a basic miner, it takes more time than that to make your $250 into $3000. If ever someone is telling you that you can make instant money with bitcoin that is probably a scam, there is no easy money nowadays it takes hard work and patience to earn. Don't believe what other people say, do your own research to prevent getting scammed.