A road crosses a railroad track at right angles. A pickup truck traveling 30mph crosses the intersection 20 minutes before a greight train traveling 60mph

railroad-track

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A road crosses a railroad track at right angles. A pickup truck traveling 30mph crosses the intersection 20 minutes before a greight train traveling 60mph. How fast is the distance between the train and the truck changing 10 minutes after the train passes through the intersection. If someone could at least give me a way to start this it’d be great, I’m completely stuck.

Answer:

Make right triangle ABC where one leg is the pickup truck’s distance and the other is the trains. The hypotenuse being the distance apart.

This says it’s calculus but I don’t think it is so I might be wrong and likely made a mistake by overlooking a variable but by using the Pythagorean theorem, I concluded that sqrt((30x+10)^2+(60x)^2}
(x is time in hours)