Final answer:
To find the point at which the two boats are closest together, we can use the Pythagorean theorem and take the derivative of the distance function.
Step-by-step explanation:
To find the point at which the two boats are closest together, we need to calculate the distance between them at different times. Let's assume that t hours have passed since 1:00 pm. The boat traveling south will have traveled a distance of 20t km, and the boat traveling east will have traveled a distance of 15 km. We can use the Pythagorean theorem to find the distance between the two boats:
d = sqrt((20t)^2 + 15^2)
Next, we can take the derivative of the distance function with respect to t and set it equal to zero to find the minimum distance:
d' = 0
Solving this equation will give us the value of t when the two boats are closest together.