You think you’re good in mental calculations? Watch Arthur Benjamin, one of the most amazing mental calculators of our time. Mr. Benjamin can square up to 4-digit number faster than a calculator. He can also square up to 5-digit numbers mentally. In addition, he can also determine mentally the day of the week that you are born.
Watch the 15-minute video of Mr. Benjamin the TED Talk titled Benjamin: A performance of Mathemagic.
Benjamin is the co-author of Secrets of Mental Math which is about the secret of rapid mental calculations. He is also the author of Proofs that Really Count: The Art of Combinatorial Proof .