Temporary float

Question

What's the difference between these two codes written in c(what difference "(float)" is making)

#include <stdio.h>

int main() {

int a=81, b=39, c,d,e;
c=a+b;
printf("Answer to the function (a+b) = %d\n",c);
d=(float)a/b;
printf("Answer to the function (a/b) = %d\n",d);
e=a-b;
printf("Answer to the function (a-b) = %d\n",e);
return 0;
}
and this

#include <stdio.h>

int main() {

int a=81, b=39, c,d,e;
c=a+b;
printf("Answer to the function (a+b) = %d\n",c);
d=a/b;
printf("Answer to the function (a/b) = %d\n",d);
e=a-b;
printf("Answer to the function (a-b) = %d\n",e);
return 0;
}