keil mcbstm32f400 core utilization

I am measuring acceleration continuously using keil mcbstm32f4 development kit and calculating the time dt for integrating acceleration to get velocity. Velocity= summation of a*dt.Since dt is very small=8.3us between 2 acceleration measurements.The code for calculation is attached .
I am performing these calculations in a loop continuosly but in real time the velocity is not showing correct, for example in z axis for 9.8 m/s2 or 1g it should show 9.8x1=9.8m/s velocity but it is increasing very slowly as the stm32f400 is not able to do that many calculations (1/8.3us=1000000/8.3 =calculations) fastly in 1 s. So i want to know how to increase the speed of operation by utilizing all the cores.

while (1)
        {


  float x1=(acc.x * 25/1000)/2.4489;///2.4489;
  float angx1=(ang.x * 25/1250);
  float y1=(acc.y * 25/1000)/2.4489;///2.4489;
             float angy1=(ang.y * 25/1250);
                           float z1=(acc.z * 25/1000)/2.4489;///2.4489;
                            float angz1=(ang.z * 25/1250);


                              float x2=(acc.x * 25/1000)/2.4489;
                                                                    float y2=(acc.y * 25/1000)/2.4489;
                                                                    float z2=(acc.z * 25/1000)/2.4489;

                                                                    float x3=(acc.x * 25/1000)/2.4489;
                                                                    float y3=(acc.y * 25/1000)/2.4489;
                                                                    float z3=(acc.z * 25/1000)/2.4489;
//
                                                             float navgx=0;
                                                                    navgx=(x1+x2+x3)/6;

                                                           float navgy=0;
                                                                    navgy=(y1+y2+y3)/3;

                                                           float navgz=0;
                                                                    navgz=(z1+z2+z3)/3;

                                                                        velx=velx+(navgx*0.000083);
                                                                        vely=vely+(navgy*0.000083);
                                                                         velz=velz+((navgz-9.81)*0.000083);

                }