1. The problem statement, all variables and given/known data A supersonic jet traveling at Mach 3.00 at an altitude of 20 000 m is directly over a person at time t ϭ 0, as in Figure P17.43. (a) How long will it be before the person encounters the shock wave? (b) Where will the plane be when it is finally heard? (Assume that the speed of sound in air is 335 m/s.) 2. Relevant equations 3. The attempt at a solution So I figured it would just be the time for sound to travel from the plane to the ground, or t = d/v = 20 000m/355m/s, but that gives me 59.7s, and the answer book says 56.3s. What am I doing wrong?