Tukukkk

I am trying to get 20 in the variable nm. But it is returning 19.

How do I fix it? And what is causing this problem?

#include <stdio.h>

#include <cs50.h>

#include <math.h>



int main(void)

{



    float m;



    int n = 0;

    do {

         m = get_float("Enter:");



        }while(m < 0);

    int nm =(m * 100 );

    while(nm >= 25 ){

        nm = nm - 25;

        n = n + 1;



    }



    printf("%in",n);

    printf("%in", nm);

}

A 32-bit float can encode about 2³² different values exactly. Due to the binary nature of the typical float, 4.2 is not one of them.

Instead m has the value of 4.1999998...

// closest float

4.19999980926513671875

// hoped for value

4.2

// next closest float

4.200000286102294921875

Multiplexing by 100 incurs some rounding and the best answer to m*100 is then 419.999969482421875.

int nm =(m * 100 ); results nm == 419 as assignment of a float to int truncates the fractional portion away.

Consider rounding to the nearest integer rather than truncating via int assignment and use double constants.

#include <math.h>



// int nm =(m * 100 );

int nm = lround(m * 100.0);

// or 

int nm = round(m * 100.0);