1. The problem statement, all variables and given/known data [PLAIN]http://www.antonine-education.co.uk/Physics%20A%20level/Options/Module_8/Topic_6/cars_4.gif [Broken] What is the speed of sound, relative to: A - B - C - 2. Relevant equations None. 3. The attempt at a solution For B, since B is a stationary reference point, the speed of sound relative to B should 330ms^-1 For A, I thought it should be 360, since A is a moving reference in the same direction as the speed of sound. Meaning A = 330+30=360 For C, I thought it should be 300, since the moving reference is moving in the opposite direction to the speed of sound, making B=330-30=300 My answers for A and C are wrong, however. Help!