How to calculate the volume of glass juice? - c

Question

The radius of the upper part r1 and lower part r2 is given. If the height of the glass is h and height of the juice is p what is the volume of the juice in the glass? For some input-output is wrong:
#include <stdio.h>
#include <math.h>
int main() {
int r1, r2, h, p;
scanf("%d %d %d %d", &r1, &r2, &h, &p);
//for juice height p we will find out the radius r3
float r3 = ((r1 * p) / h); //calculating r3 by percentage formula
float v = ((M_PI / 3) * 3 * ((r3 * r3) + (r2 * r2) + (r3 + r2)));
printf("Volume : %f\n", v);
return 0;
}
EDIT: After I changed the all int to double still for some input output is wrong for an example for input 5 2 3 2 the answer should be 58.64.

Answer 1

Integer division yields an integer result - 1/2 == 0, 5/2 == 2, etc., so ((r1*p)/h) is not giving you the right value.
You should declare your inputs as double instead of int and use %lf instead of %d to read them:
double r1,r2,h,p;
scanf("%lf %lf %lf %lf",&r1,&r2,&h,&p);
You'll also want to declare r3 and v as double instead of float.

Answer 2

Besides the errors shown in John Bode's answer, the posted code is using the wrong formulas to calculate the volume.
#include <stdio.h>
#include <math.h>
// M_PI is not a standard macro
#if !defined(M_PI)
#define M_PI 3.14159265358979323846
#endif
int main(void)
{
// Given the following calculations, I'd use a floating-point type
// to store the values.
double r1, r2, h, p;
// The format specifiers need to be changed accordingly.
scanf("%lf%lf%lf%lf", &r1, &r2, &h, &p);
// To extimate the radius of top surface of the juice, we can't forget
// the radius at the bottom of the glass (it's not zero!).
double r3 = r2 + ((r1 - r2) * p) / h;
// The volume of the conical frustum can be calculated with a formula different
// from the posted one and we need to consider the height of the juice.
double v = M_PI * p * (r3 * r3 + r3 * r2 + r2 * r2) / 3.0;
printf("Volume : %f\n", v);
return 0;
}