For batching 1:2:4 concrete mix by volume is given; weight of cement is given as 50kg and density of cement is taken as 1440kg/m‌3 then, volume of cement = {weight of cement (50 kg)/density of cement (1440)} = 35 litre therefore; volume of fine aggregate = 70 litre and volume of coarse aggregate = 140litres since ratio of concrete mix is given as 1:2:4 Note: If concrete mix has been given as 1:2:4 by weight then, weight of cement: weight of fine aggregate: weight of coarse aggregate = 50:100:200