Your post could be improved to make a lot more sense. I assume you want to know what volume of 4.0 M(not m) is needed to make 2.5 dm^3 (not dm) of 0.25 M (not m).
dm^3 1 x M1 = dm^3 2 x M2
dm^3 x 4 = 2.5 dm^3 x 0.25
Calculate the volume of 4.0m hydrochloric acid that is required to make 0.25m of the volume of 2.5dm of the solution
4 answers
You need to understand the difference between m and M in chemistry. m stands for molality = mols solute/kg solution while M stands for molarity = mols solute/L of solution (or in your convention M = mols solute/dm^3 solution).
You teachers are rude. can you try to be helpful and NICER? because in a minute this is going to be a issue!
No offense btw