problem 35 saving Calculator

Hi, I have problem with this task. I tried to use both formular and the loop to solve it, but it still has some case. I use C in this task. And even I tried to calculate this task by a calculator, the result seem to be same to me. this is my code, can you help me please

#include <stdio.h>
#include <math.h>

int main(void) {
int a;
double start[100], rate[100], sum[100];
double canso[100], out[100], tren[100], duoi[100];
scanf("%d", &a);
for(int i=0; i<a; i++)
{
    scanf("%lf %lf %lf", &start[i], &sum[i], &rate[i]);
// out[i]=0;
}
for(int i=0; i<a; i++)
{
//    canso[i]=log(1+rate[i]);
/*  
    tren[i]=log10(sum[i]/start[i]);
    printf("%lf ", rate[i]);
    canso[i]=(rate[i]/100)+1;
    printf("%lf ", canso[i]);
    duoi[i]=log10(canso[i]);
    printf("%lf ", duoi[i]);
    out[i]=tren[i]/duoi[i];
    printf("%lf %lf %lf %lf ",tren[i], duoi[i], canso[i], out[i]);  //I use the formular to solve
    printf("%.0lf ", ceil(tren[i]/duoi[i]));
}
*/
    rate[i]=rate[i]/100;
    // printf("%f ", rate[i]);
    out[i]=start[i]*(rate[i])+start[i];     //use the loop to solve
    int count=1;
do{
    out[i]+=out[i]*(rate[i]);
    count++;
    //printf("%f ", out[i]);
}
while(out[i]<sum[i]);
printf("%d ", count);
count=1;
}
return 0;
}