distance changing between two moving objects

Question

Brad is traveling one mile east of a 90 degree intersection traveling east at 30 mph Abby is 5 miles north of the intersection traveling south at 18 mph ten Minutes later how fast is the distance between the two changing?

Answer 1

the two vehicles are at (x,0) and (0,y) and the distance separating them is z = √(x² + y²).

 

dz/dt = ½[x²+y²]^-½(2x dx/dt + 2y dy/dt)

 

dx/dt is 30 & dy/dt is 18 and all you have to do is to evaluate dz/dt when x=1, y = 5.

 

You can take it from here.