In this Cyberchase video clip, Harry is auditioning for a talent show with a subpar magic act. One audience member continuously heckles him until Harry pulls him up on stage. Using ratios, proportions, and a piece of string, Harry demonstrates that you can use the size of certain body parts to predict the lengths of others. For example, he shows the audience if you measure three times around someone's head, it is usually equivalent to their height and arm span.