Mental WizardryTo view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video04/16/2013April 16, 2013Gert Mittring has broken world records for mental calculation no less than nine times. He's faster than a calculator, figuring out square roots of huge numbers in the blink of eye. Doing sums, he says, relaxes him.https://p.dw.com/p/18GNdAdvertisement