Answer:
The time it takes Ms. Croft to reach the cruise ship by speedboat = 6.11 hours
The time it takes Ms. Croft to reach the cruise ship by helicopter = 6.25 hours
since it takes less time for Ms. Croft to reach the cruise ship by taking the speedboat, her best choice to retrieve the artifact is to take the speedboat.
Explanation:
The given parameters are;
The elapsed time by which Ms. Croft missed the boat = 5 hours
The speed of the cruise ship = 528 mi/day
The speed of the speedboat = 100 miles in 2.5 hours
The speed of the helicopter = 90 mph
The time it would take Ms. Croft to arrive at the harbor = 3.5 hours
Therefore, we have;
The cruise ship's speed = 528 miles per 24 hours = 528/24 mph = 22 mph
The location of the cruise after the first 5 hours = 5 × 22 = 110 miles
The speed of the speedboat = 100 miles per 2.5 hours = 100/2.5 = 40 mph
By traveling with a speed boat
The time at which Ms. Croft will intercept the cruise ship is given by the following relation;
40 mph × t = 22 mph × t + 110 miles
Which gives;
40 mph × t - 22 mph × t = 110 miles
18 mph = 110 miles
t = 110 miles/(18 mph) = 55/9 hours ≈ 6.11 hours
By taking the helicopter, we have;
Upon arrival at the harbor, after 3.5 hours, we find
90 mph × t = 22 mph × t + 22 mph × 3.5 hours + 110 miles
90 mph × t - 22 mph × t = 22 mph × 3.5 hours + 110 miles
68 mph × t = 77 miles + 110 miles = 187 miles
t = 187 miles/(68 mph) = 11/4 hours = 2.75 hours
The total time it takes Ms. Croft to reach the cruise ship by taking the helicopter = 3.5 + 2.75 = 6.25 hours
Therefore, since it takes less time for Ms. Croft to reach the cruise ship by taking the speedboat, her best choice to retrieve the artifact is to take the speedboat.