Renee is staying in a cottage along a beautiful and straight shoreline. A point $Q$ on the shoreline is located 3 kilometers east of the cottage, and an island is located 2 kilometers north of $Q$ (see image below). Renee plans to travel from the cottage to the island by some combination of walking and swimming. She can start to swim at any point $P$ between the cottage and the point $Q$. If she walks at a rate of $3 \mathrm{~km} / \mathrm{hr}$ and swims at a rate of $2 \mathrm{~km} / \mathrm{hr}$, what is the minimum possible time it will take Renee to reach the island?
Enter an exact answer or round to the nearest hundredth of an hour.
So the minimum possible time it will take Renee to reach the island is approximately \(1.5 + 1.92 = 3.42\) hours. Therefore, the final answer is \(\boxed{3.42}\) hours.
Step 1 :Let's denote the distance from the cottage to the point P where Renee starts swimming as \(x\) (in kilometers). Then the distance from P to Q is \(3 - x\), and the distance from P to the island is the hypotenuse of a right triangle with sides \(3 - x\) and 2, which is \(\sqrt{(3 - x)^2 + 2^2} = \sqrt{x^2 - 6x + 13}\) by the Pythagorean theorem.
Step 2 :The time it takes Renee to walk from the cottage to P is \(x / 3\) hours, and the time it takes her to swim from P to the island is \(\sqrt{x^2 - 6x + 13} / 2\) hours. So the total time is \(T = x / 3 + \sqrt{x^2 - 6x + 13} / 2\).
Step 3 :We want to minimize T. To do this, we can take the derivative of T with respect to x, set it equal to zero, and solve for x. The derivative is \(1 / 3 + (x - 3) / (2 \sqrt{x^2 - 6x + 13})\), and setting this equal to zero gives \(x = 3 / 2\).
Step 4 :Substituting \(x = 3 / 2\) into the expression for T gives \(T = 3 / 2 / 3 + \sqrt{(3 / 2)^2 - 6 * 3 / 2 + 13} / 2 = 1 / 2 + \sqrt{1 / 4 + 1 / 2 + 13} / 2 = 1 / 2 + \sqrt{14.75} / 2\).
Step 5 :So the minimum possible time it will take Renee to reach the island is approximately \(1.5 + 1.92 = 3.42\) hours. Therefore, the final answer is \(\boxed{3.42}\) hours.