Question

#include <stdio.h>
#include <stdlib.h>
#define calc(a,b) (a*b)/(a-b)
void calculate(){
    int a = 20, b = 10;
    printf("%f\n", calc(a+4,b-2));//output 0.00000
}

what to do to print the actual answer, 4.83.

Answer 1

The problem here is with your datatypes which are ints, not with format-specifiers. Integer division is always truncated to the whole numbers. You should consider changing your variables to float instead of int.

Try this:

#include <stdio.h>
#include <stdlib.h>
#define calc(a,b) (a*b)/(a-b)
void calculate(){
    float a = 20.0f, b = 10.0f;
    printf("%f\n", calc(a+4,b-2));//output 0.00000
}