The problem has a strange answer . . .
A north-south highway intersects an east-west highway at point P.
A car crosses P at 10:00 am, traveling east at a constant speed of 20 km/hr.
A car north of P, twenty minutes later passes that same point, traveling south at 60 km/hr.
Find the approximate the minimum distance between the automobiles.
Answer: 6.3 km
At 10:00, car drives east from at 20 km/hr.Code:| | 20/3 Q 20t R P o - - - o - - - - o | * | * 60t | * x | * | * S o
By 10:20, it has moved to point km.
In the next hours, it has moved km to point
In the same hours, car moves from to at 60 km/hr.
Let = distance between the cars,
To minimize , set and solve.
We have: .
. . . The minimum distance occured two minutes before 10:20.
At 10:18, car was 6 miles east of point
At 10:18, car was 2 miles north of point
Their distance was: .