A truck moving at 36 m/s is in the process of being passed by a police car moving at 45 m/s in the opposite direction. If the frequency of the siren relative to the police car is 500 Hz (stationary frequency), what is the frequency heard by an observer in the truck as the police car approaches the truck, just before passing

i had this question and the answer was 3.15 miles.

martina travels from school to her mom's office. from there, she walks to school. after school, she walks to the library and then to a friends house before finally ending back at home. find martina's total distance traveled.

a) 0 miles  

b) 0.4 miles  

c) 1 mile  

d) 3.15 miles