Question 255994
A boardwalk is parallel to and 210 ft inland from a straight shoreline.
 A man is standing on the boardwalk, exactly 750 ft across the sand from his beach umbrella, which is right at the shoreline.
 The man walks 4 ft/s on the boardwalk and 2 ft/s on the sand.
 How far should he walk on the boardwalk before veering off onto the sand if he wishes to reach his umbrella in exactly 4 min 45 sec.
:
Work this in seconds; 4 min 45 sec = 285 seconds
:
Find out how long to arrive at his umbrella, at the two extremes
:
1.Heading directly to umbrella across the sand 750ft away
{{{750/2}}} = 325 sec
:
2. Walking the board-walk to a point directly in front of the umbrella then
heading across the sand 210 ft
:
Find the boardwalk distance (b), one leg of a right triangle
b = {{{sqrt(750^2 - 210^2)}}}
b = 720 ft, the dist on the board walk
:
total time = time on b.w + time on sand
 t = {{{720/4}}} + {{{210/2}}}
t = 180 + 105 
t = 285 sec which is 4 min 45 sec
:
Answer: 720 ft on the boardwalk