What is the only possible resultant magnitude that you can obtain out of the following choices?

If you are only adding vectors of length 20 and 40 units, the only possible resultant magnitude that you can obtain out of the following choices is 37. So the important thing to know about vectors is that the minimum resultant magnitude only occurs when the vectors are opposite, giving 20 units.

When the vectors are aligned and give 60 units, then the maximum resultant would occur. As the minimum and maximum magnitudes are the two extremes, there are many other possiblities in between these two values.