is it necessary to type cast from float to double in c code example

Example 1: type change in c

#include <stdio.h>

main() {

   int sum = 17, count = 5;
   double mean;

   mean = (double) sum / count;
   printf("Value of mean : %f\n", mean );
}

Example 2: int to double c

int vIn = 0;
double vOut = (double)vIn;