Classical Runge-Kutta Method  
                      The derivation of fourth order Runge-kutta methods involve tedious calculations. It transpires that with R=4, the fourth order and no higher can be obtained. The well-known fourth order classical Runge–Kutta method is given by  
                        
                        
                      
                        
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                          (3.30)  | 
                         
                                               
                        
                      Remark:  We have seen that there exists an R-stage method of order R and none of order greater than R for  . We have the following result that relates the no. of stages in the Runge-Kutta process with the order of the method:   |