Question: how to calculate dlbd of sand?
Answer: DLBD method to determine material requirement for Nominal Concrete Mix (M20 – 1:2:4)
Step-1: ... 
Step-2: ... 
So, Sand required = 0.07*1600 = 112 kgs.
and Aggregate required = 0.14*1450 =203 kgs.
Step-3: ... 
Empirical method to determine material requirement for Nominal Concrete Mix:-
Step-1: