A divided wall column has been modeled as a Petlyuk column with no heat transfer across the column wall. The feed to the column has been generalized as a mixture of saturated liquid and vapor (0 < q < 1). The pinch compositions at connection points, the Fenske equation and the Gilliland correlations, which have been commonly used by previous investigators to design divided wall columns, have not been applied. In contrast, a shortcut method based on Underwood's equations has been introduced. Moreover, it is shown that the split of the internal reflux over both sides of the middle wall of the column is bounded and a method for choosing the proper value of the split ratio is suggested. This is a novel approach not attempted before by investigators.