⦁ Motorcycle A is moving north at 60kph, and motorcycle B is 120 km north of A is heading west at 50 kph. At what rate are they approaching or separating at the end of 1 hour? At the end of 2 hours?

Answer 1

the courses of the motorcycles are perpendicular

draw a diagram to see the right triangle that is formed by the courses

the positions of the motorcycles change from start to one hour and two hours

the distance (D) between them is the hypotenuse of the triangle(s)
... A and B are their distances from the intersection of their courses

D^2 = A^2 + B^2

differentiating ... 2 D dD = 2 A dA + 2 b dB

plug in the known values to solve for dD at 1 hr and 2 hrs