Hello candidate,

The solubility of the salt refers to the mass of the salt which will dissolve per 100 mL of solvent.

So in the given question is mentioned that, 45 grams of potassium nitrate is needed to make 55 gram of saturated solution. So the solvent content in the solution is is about out 55 grams compared to the solute.

Hence, the solubility of the saturated solute is equal to 45 per 100 ml.

Have a good day.