Finding the Distance Between Two Towers. Orienteering
First off watch the Youtube video at http://youtu.be/n9s8FUG2S64. This sets the problem up. This is a basic orienteering problem.
This works better with students if you take them out in a bus to actually collect their own data. When I have done this problem with students. I ask them to guess the distance between the two towers and have them plot that guess on a number line with sticky notes. Then I break them into teams and tell them that whoever is closest to the actual answer both by guess, measurement, and mathematical proof wins a candy bar of their choice.
DO NOT CHECK THE TWO BOXES. THIS WILL REVEAL THE ANSWER!! TRY TO MODEL THE PROBLEM ON YOUR OWN FIRST!!!