This is a good one.  I am a computer programmer, and I hate maths.  Trachtenberg is a great technique to do lightning fast calculations.  At worst, you can amaze your friends or make children feel inadequate as they toil away with a paper and pen.

The Trachtenberg Speed System of Basic Mathematics is a revolutionary system for calculating and teaching basic math. Children, who had repeatedly failed in arithmetic until their parents sent them to learn this method, were able to perform amazing calculations within seconds. In one demonstration, a ten year old child, when asked to multiply 5132437201 times 452736502785, simply wrote on the blackboard the answer, 2323641669144374104785, in seventy seconds. He never set up the basic and familiar line by line chart, multiplying and adding each row of numbers. Instead, he just wrote down the answer without any of the intermediate steps.

To demonstrate his method, Trachtenberg chose children who were doing poorly in their school work. These were children used to failure, shy and withdrawn; or at the other extreme, rebellious and unmanageable. The children's responses to the new, easy way of doing arithmetic was immediate. They found it delightfully like a game. The feeling of accomplishment soon made them lose their disagreeable traits. Equally important were the by-products the pupils attained while learning this new system. As these youngsters became proficient in handling numbers, they began to spurt ahead in all their studies.

Their IQs went up as well! Not only did the child learn to compute, but his IQ also went up. Since all problems were worked out in his head, he developed an excellent memory and his ability to concentrate was increased. The Trachtenberg system, once learned, can take the drudgery out of the arithmetic that is part of everyone's daily stint. Experts believe that the Trachtenberg system could have far-reaching effects on education and science.