There is only one one in one one, but there are two ones in eleven. And there are no "ones" in one one if you are counting the "s". so there is one, one in one :)
1 plus 1 = 2 because 1 thing and another thing is 2 thingsthink abstract; like (example) 1 sandpile + 1 sandpile = 1 sandpile. Or 1 glass of water plus one glass of water = 1 bigger glass of water.