The problem of a balanced, planar or axisymmetric, supersonic jet impinging normally on a flat surface has been considered based on an inviscid theory. The object of the study was to provide a rational model for calculating shock-interference heating as produced by a type IV shock-interaction pattern. The unwanted singularity at a low supersonic Mach number peculiar to scheme I of the one-strip formulation of the method of integral relations, as observed by South and by Gummer and Hunt, was successfully removed by the application of the scheme III of the one-strip formulation of the method of integral relations. The resulting simultaneous nonlinear algebraic equations were easily solved iteratively by the Newton-Raphson method. Sensitivity of the solution on various approximating functions employed was extensively investigated. Unlike the findings reported by Gummer and Hunt, solutions that satisfy all well-posed boundary conditions can be obtained by the one-strip formulation. Results indicate that, for the planar case, a rational engineering solution for the stagnation-point velocity gradient (and hence the peak heat-transfer rate) has been obtained. For the axisymmetric case, however, solutions appear to be not quite converging. A two-strip formulation based on the method of integral relations is also included.