While John is traveling along a interstate highway he notices that the mile marker reads 242 km. John travels until he reaches the 147km marker and then retraces his path to the 161 km marker. What is the John's resultant displacement from the 242 km marker answer in units km

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.