Program is accepting radius of circle and using below formula

area of circle : A=πr2

Circumference of circle = 2πr

Volume of Sphere = V=4/3 πr3

```
//Program name: Calculate Area, Circumference of Circle and Volume of sphere
#include<stdio.h>
#include<conio.h>
#define pi 3.14 //constant decleration
void main()
{ int r,op;
float c_area,c_circumference,c_Vsphere;
printf("\nEnter Radius of Circle to Calculate area, Circumference : ");
scanf("%d",&r);
printf("\n\t1) Area of Circle. \n\t2) Circumference of circle.\n\t3) Volume of Sphere.");
printf("\n\n\tSelect Option : ");
scanf("%d",&op);
switch(op)
{ case 1: c_area=(float) pi*r*r;
printf("\n\n\tArea of Circle = %.2f ",c_area);
break;
case 2: c_circumference=(float) 2*pi*r;
printf("\n\n\tCircumference of circle = %.2f ",c_circumference);
break;
case 3: c_Vsphere=(float) 4/3*pi*r*r*r;
printf("\n\n\tVolume of Sphere = %.2f ",c_Vsphere);
break;
default: printf("\n\t Invalid option ");
}
}//main
```

#### Output

```
Enter Radius of Circle to Calculate area, Circumference : 7
1) Area of Circle.
2) Circumference of circle.
3) Volume of Sphere.
Select Option : 1
Area of Circle = 153.86
Select Option : 2
Circumference of circle. = 43.96
Select Option : 3
Volume of Sphere. = 1436.03
```