Required information
Sheena can row a boat at $3.20 \mathrm{mi} / \mathrm{h}$ in still water. She needs to cross a river that is 1.20 mi wide with a current flowing at $1.70 \mathrm{mi} / \mathrm{h}$. Not having her calculator ready, she guesses that to go straight across, she should head upstream at an angle of $25.0^{\circ}$ from the direction straight across the river.
In order to go straight across, what angle upstream should she have headed?

Step 1 ：The problem is asking for the angle Sheena should head upstream to go straight across the river. This is a problem of relative velocities. The velocity of the boat relative to the river current determines the path the boat will take.

Step 2 ：We can solve this problem by using trigonometry. We know the speed of the boat in still water (\(v_{boat} = 3.2\) mi/h) and the speed of the current (\(v_{current} = 1.7\) mi/h). We can consider these as two vectors at right angles to each other. The resultant vector, which is the actual path of the boat, should be straight across the river.

Step 3 ：We can use the tangent of the angle between the boat's direction and the direction straight across the river, which is equal to the speed of the current divided by the speed of the boat in still water.

Step 4 ：So, we need to calculate the arctangent of the ratio of the speed of the current to the speed of the boat in still water.

Step 5 ：The calculated angle is approximately 27.98 degrees. This is the angle upstream that Sheena should have headed in order to go straight across the river.

Step 6 ：Final Answer: The angle upstream that Sheena should have headed in order to go straight across the river is approximately \(\boxed{27.98}\) degrees.