Halloween_Candy(Code_Coach_Problem)

Question

I made a code to solve the halloween candy problem. It passed the first two tests but failed in the remaining 3 test cases. As they are hidden,I can't understand what's wrong with my code.
My_code:

#include <stdio.h>

int main() {
int houses;
float a,b;
scanf("%d", &houses);
if(houses>=3){
a=(float)2/houses;
b=(float)a*100;
printf("%0.0f",b);
}
return 0;
}

Answer 1

Output should be rounded up to the nearest integer.

#include <math.h>
...
printf("%0.0f",ceil(b))

Answer 2

Ceil rounds float up to the next int.

Answer 3

Simba It worked!
But how did it worked!?
What is the use of ceil!?