You are a Book lender who strangely lends books of equal length and difficulty ever time. You have people who you lend your books to, but you want to find out who is the fastest reader of the group and who is the slowest reader of the group.
This is the situation.
There are ten people who all read books at different speeds and they will always read the books you give them in the same amount of time that they read all the other books.
When you lend a book because of the way your book lending system is set up, the book is shared between three people. Meaning when the first person receives the book they will read it in the time it takes them, then give it to the next person to read, then they will give the third and last person the book to read and they will return it to you.
You as the book keeper get to choose which three people get the book at anytime. The only information you are given is the amount of time it took all three of your selected people too read the book(the sum of all three of their reading times)
All of the people are perfect actors so they will never change the amount of time that it takes them to read a book and there will be no transition time between giving the book to each other.
You have an infinite amount of books to lend so you can take as many steps as you would like in which you select three of ten each time and see the sum of those three's reading time.
Remember you are trying to find the fastest and the slowest reader by lending these books.
So how would you do it?