So I just answered this question and it was wrong. May someone clear this up for me?
So, you are adding two vectors of length 20 and 40 units. What is the only possible resultant magnitude that you can obtain out of the following choices? (18, 37, 64 or 100).
I chose 64 because if you add the two vectors together, they come out as 60, right? So it is a possible magnitude. But the answer they have is 37, which I do not understand.

Question

So I just answered this question and it was wrong. May someone clear this up for me? 
So, you are adding two vectors of length 20 and 40 units. What is the only possible resultant magnitude that you can obtain out of the following choices? (18, 37, 64 or 100).
I chose 64 because if you add the two vectors together, they come out as 60, right? So it is a possible magnitude. But the answer they have is 37, which I do not understand.

lastdaywork · Answer

Let the magnitude of the two vectors be 'a' and 'b'

Then the magnitude of their vector sum lies between |a-b| and a+b

vincent-lyon.fr · Answer

If you walk 40 paces in one direction and 20 paces in a new (possibly same) direction, you will NEVER be able to find yourself at 64 paces from where you started in the first place. Don't you think?