Floating point exception CS50 readability assignment - c

Question

I'm facing some problems regarding the Floating point exception error because previously when i printed the variables individually so i wasn't sure what went wrong. Down below is the code i have written so far. I'm not sure what cause the error as i am pretty sure i'm not dividing by zero.
#include <stdio.h>
#include <cs50.h>
#include <ctype.h>
#include <string.h>
#include <math.h>
int main(void)
{
//promt user for text
string n = get_string("Text: ");
int sumletters = 0;
int sumdots = 0;
int sumspaces = 1;
for (int i = 0; i < strlen (n); i++ )
{
if (n[i] >= 'A' && n[i] <= 'z')
{
sumletters = sumletters + 1;
}
if (n[i] == ' ')
{
sumspaces = sumspaces + 1;
}
if (n[i] == '.' || n[i] == '?' || n[i] == '!' )
{
sumdots = sumdots + 1;
}
float L = sumletters / (sumspaces / 100);
float S = sumdots / (sumspaces / 100);
int index = round ((0.0588 * L) - (0.296 * S) - 15.8);
if (index < 1)
{
printf ("Before grade 1\n");
}
{
printf ("Grade 16+\n");
}
else
{
printf ("Grade %i", index);
}
}
printf ("\n");
}

Answer 1

This is the part at fault:
sumletters / (sumspaces / 100)
sumspaces / 100 uses integer division so it will almost always be 0. You can refactor your code to use floating point division by simply distributing the division:
sumletters / sumspaces * 100

Answer 2

The below is integer division and the quotient is often zero as int math discards the fraction.
int sumspaces;
...
sumspaces / 100
The below can result in int division of 0.
int sumletters;
...
// v---------------v might be 0
sumletters / (sumspaces / 100);
Floating point exception error ... i am pretty sure i'm not dividing by zero.
For various reason of a common error handler, int division by zero may be reported as a floating point exception.
As with many operations were the result type is not in the operation, but only the assignment, such problems are common.
Instead, insure the math uses the destination type.
// v---------------v int division
// float L = sumletters / (sumspaces / 100);
float L = sumletters / (sumspaces / 100.0f);
// ^------------------^ At least float division
Aside: No good reason to use float types here, just use double.
Notice that code uses double math, and not float math in:
// v----v v---v v--v double constants
round ((0.0588 * L) - (0.296 * S) - 15.8)
// ^---^ double function