Final mixture remain 10 kg. Lets assume that x kg of pure sand was added. You also have to assume that Initia mixture is homogeneous and when we take out out x kg, the % of clay and sand remains same in that 10-x

Amount of Mixture% SandAmount of Sand

Initial Mixture10-x.3=.3(10-x)

Pure Sandx1x

Final Mixture10.55

10kg of a mixture contains 30% sand and 70% clay. In order to make the mixture contain equal quantities of clay and sand. how much of the mixture is to be removed and replaced with pure sand?