There are two flasks M and N containing 130 ml and 180 ml of two different concentrations of acid. Now 'x' ml is withdrawn from each flasks, and then the amount withdrawn from M is added to N and vice versa. Finally the concentrations found to be equal in both the flasks. Find x?

Let a% and b% be the concentrations of M and N respectively => Initial volumes of acid in the solutions M and N are 130a and 180b respectively. Final volumes of acid in the solution after transferring x ml from each of the flasks to the other flask are 130a-ax+bx and 180b-bx+ax. Final concentrations are equal => (130-ax+bx)/130 = (180b-bx+ax)/180 On solving this equation you get the value of x as 75.48 ml.