A train is heading due west from St. Louis. At noon, a plane flying horizontally due north at a fixed altitude of 4 miles passes directly over the train. When the train has

Question

traveled another 5 miles and is going 500 mph. At that moment, how fast is the distance between the train and the plane increasing?

Is the answer 5.65 miles away.

Answer 1

Something is not right with this question.
Your train is going 500 mph ?????

I think you want that to be the speed of the plane. How fast is the train going?

your answer is a "distance", it asked "how fast is the distance between them increasing" which is velocity.

Please check the wording of this great Calculus question.