Two Planes approach each other head-on. One plane has a speed of 800 km/h and the other has a speed of 900 km/h and they spot each other when they are initially 15 km apart. How much time in seconds do the pilots have to take evasive action?

Answer 1

they are headed toward each other at
(800+900) /(3600) km/s
= .4722 km/second
15 km = .4722 t
t = 31.8 seconds