Minimum Distance Between Two Cars

Author:
BHNmath

Problem

A north-south highway intersects an east-west highway. The red vehicle crosses the intersection, travelling east at a constant speed of 60 km/h. At the same instant, the blue vehicle is 5 km north of the intersection, travelling south at 80 km/h. Find the time when the two vehicles are closest to each other and the distance between them at that time.