finding SI using funtion

#include<stdio.h>
#include<conio.h>
void main()
{float interset(float,float,float);
float si,p,r,t;
printf("enter p,r,t");
scanf("%f%f%f",&p,&r,&t);
si=interset(p,r,t);
printf("interset is :%f",si);
getch();
}
float interset(float p,float r,float t)
{float si;
si=((p*r*t)/100);
return si;
}