You have a cup, it has a mass of 1 Kg. In the cup is a liquid, with a mass of 1.5 Kg. the Cup (and liquid) are on a weight scale (call it X). We have another object, with known volume (call it V), attached to a spring-scale from upwards (call it Y). The object was put inside the liquid (not floating), X reads 7.5*g N, Y reads 2.5*g N, what is the density of the liquid. Now, what most people i know did is that they said : The weight of cup and liquid = (1+1.5)*g = 2.5*g N And since scale X reads 7.5*g N, then the real (not apparent) weight of the object must be 5*g N (and they start to solve from there). What i have made is that i drew a free body diagram, and i reached the conclusion that the real weight of the object is 7.5*g N. Who do u think is right ? Thanks in advance.