why I cannot compare the value?

[timhxf]

this a simple program to compare two numbers, but it cannot display the correct result, what I got is always "0.00". why?

#include<stdio.h>
double small(double x,double y);
int main(void)
{
    double x,y;
    printf("ple enter number");
    scanf("%f %f",&x,&y);
    printf("the smaller number is %.2f", small(x,y));
    system("pause");
    return 0;
}
double small(double x,double y)
{
       if(x<=y)
       return x;
       else
       return y;
}

[Prelude]

>scanf("%f %f",&x,&y);
The scanf format modifier for double is %lf.