a milk of 80% conc. is diluted at home by the seller by adding some water to it so that milk conc. is reduced btw 65% to 70% . if 640 l of milk of 80% conc. is available how much water has been added??
the amount of water in 640 lt of milk of 80% con is 640 - 512 = 128 lt.
let the x lt of water has been added,
therefore the concentration of milk in new mixture is
let the milk concentration in new mixture is %
hope this helps you