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 you to explain how you know you're the same distance from each other?

See below.

Step-by-step explanation:

First, two of you hold the string at its opposite ends. Then you come together. the third friend will then  grab the  string approximately at it's centre and walk  away from you both loosely holding the string and adjusting his hold until both halves of the string are taut. He will now be holding the middle of the string and the 2 other friends walk away in opposite directions  with the string kept taut. When they are at the farthest point they can travel the 3 friends are now equal distances apart.

lockers 1, 4, 9, 16, 25, 40, and 49 are open

i ran through it by the other answer is wrong