You are driving south along the shore of the Mississippi River. At this point it is flowing due South. You notice a prominent radio tower right on the far shore, at a bearing of 115 degrees. You drive on for 2 miles and notice that now the radio tower appears at a bearing of 55 degrees. You figure that at this point the Mississippi river is miles wide.
Hint: Draw two right triangles, set up some equations, and solve them for the width of the river.