density in circulation

[problems123]

Im finding a average density as per our standard. Tube section is divided into 100(i = 1 to 100). steam generated is assumed by in each section by total steam flow/100). From this averagedensity (V) is calculated.

There is one more avg density calcualted, = i=1 to N density of mix,V(i)/ N+1..? If anyone could help me to understand wat is the physical significance of term N+1???