Question 193446
two cars start from the same point at the same time. One travels north at 25mph and the other travels east at 60mph. How fast is the distance between them increasing at the end of 1 hour?
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At 1 hour, the distances to the starting point are 25 miles and 60 miles, the 2 legs of a right triangle.
The distance between them is the hypotenuse is 
h^2 = {{{sqrt(25^2 + 60^2)}}}
h = 65 miles
dh/dt = 65 mph
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It can be shown with differentiation if necessary, email me via the thank you note if you need to see that.