In the midst of this chopping sea of civilized life, such are the clouds and storms and quicksands and thousand-and-one items to be allowed for, that a man has to live, if he would not founder and go to the bottom and not make his port at all, by dead reckoning, and he must be a great calculator indeed who succeeds. Simplify, simplify.
Speaking of human computers, there is a guy named Art Benjamin, he's a human calculator. He says it's a skill he learned as a kid. Now he's a math professor at Harvey Mudd. He can find the square root of a six-digit number in a few seconds. Practice.