A boat leaves a dock at 3:00 P.M. and travels due south at a speed of 20 km/h. Another boat has been heading due east at 15 km/h and reaches the same dock at 4:00 P.M. How many minutes after 3:00 P.M. were the two boats closest together? (Round your answer to the nearest minute.)

Question

radar · Answer

$$d=\sqrt{625t ^{2}-450t+225}$$ differentiate and set to 0, solve for minimum.$$5(25t-9)\over \sqrt{25t ^{2}-18t+9}$$

radar · Answer

t=9/25
t=(9/25)60=21.6 min  or 3:22 PM