Answer :

when the vectors have the same direction 

Answer:

 The magnitude of the two vectors are added as when the both the vectors are in the same direction. We can easily add the the magnitude of the given vectors by using the simplest and easiest way is that we can find the resultant of the given magnitude.

The addition of two vectors is called as the resultant of the two vectors and by using the triangle and the parallelogram method we can easily find out the resultant of he two vectors.