what is the percent by volume of isopropanol in a 90 mL solution that contains 25 mL isopropanol?

Question

Cant understand the question given by the teacher

Answer 1

% by volume means how much volume out of 100 ml is the isopropanol.  So, you have 90 mls of total solution, and of that, 25 mls is isopropanol.  The % by volume = 25 ml/90 ml (x100%) = 27.8% by volume.