The Mental Logs Magic Trick consists of Four small rods, each has a variety of numbers printed onto it and all are given to a spectator to thoroughly examine. The spectator is requested to randomly place them in a row. This done, the magician instantly writes down a total figure. The numbers showing on the rods are added together, when the total is arrived at, the magician's instant calculation is seen to be correct.
The trick is now offered to be repeated, even though this breaks the magician's code - this time though, the magician makes a prediction, the prediction is of the total of the figures on the underside of the rods, the side no one has even seen. The rods are turned over and added together, again the magician's total is correct.
Very easy to do, does not require mathematical skills and can be done anywhere & anytime, without any preparation.