[Math] Related Rates question: A man starts walking north at 4 ft/s from a point P. Five minutes later a woman starts

Question

A man starts walking north at 4 ft/s from a point P. Five minutes later a woman starts walking south at 5 ft/s from a point 500 ft due east of P. At what rate are the people moving apart 15 minutes after the woman starts walking? (Round your answer to two decimal places.)

Answer 1

The method is basically sound with one error. In your figure, you have a right triangle with leg lengths $500$ and $4800+4500$. The length of the hypotenuse of that triangle is $\sqrt{(4800+4500)^2 + 500^2}$, not $\sqrt{4800^2 + 4500^2 + 500^2}$.