10.0 mL of a solution of hydrochloric was titrated with a 0.100 mol L-1 solution of potassium hydroxide. 13.5 mL of the base was required for neutralisation. Calculate the concentration of the hydrochloric acid solution. Don't forget to round to 3 s.f. A unit is not required.
KOH + HCl --> KCl + H2O