is placed at the head of vector 
then the vector 
from the tail of vector to the head of vector represents the sum of vectors and [M2.4, M2.5, P2.2]
is: a geometric rule in which two vectors are represented by two sides of a triangle and their vector sum is represented by the third side. [M2.4, M2.5, P2.2]
states: that if the tail of vector is placed at the head of vector then the vector from the tail of vector to the head of vector represents the sum of vectors and [M2.4, M2.5, P2.2]
Compare with parallelogram rule.
Copyright 1997, The Open University