Hello, I am Year 10 student and would like to get help on the question below based on Boyle's Law. A piston with a block of mass 120 grams placed on it traps 200cm³ of air in a container. When the block is removed, the volume becomes 250cm³. Find the mass of the piston. In the question above i only know that you have to use the formula P1V1=P2V2, but i don't know how to apply it. Please can anyone help?