brickwork and mortar calculations

if you ask any site engineers the quantum of brick require per 100 cft majority of them shall answer 1350 nos needed for 100 cft of brick work. the explanation as follows: 1. size of each brick = 9"x4.5"x3".let us convert into inches as 0.75x0.325x0.25 2. hence volume of each brick = 0.0703...