Try to picture this scenario in your mind... You have a piece of string with a very large length, but you have no measurement tools. You and two of your friends are standing in a field with your string, and the three of you need to be the same distance from each other. How could you use the string to determine whether you are the same distance from each other? How does the use of the string help you to explain how you know you're the same distance from each other?