3. write a C program to find the area of circle using the formula Area = PI * r * r.

#include <stdio.h>
#include <conio.h>
void main()
{
    float pi = 3.14;
    float r, area;

    clrscr();

    printf("\n");
    printf("Enter the value of r : ");
    scanf("%f", &r);

    area = pi * r * r;

    printf("Area : %f", area);

    getch();
}

Output

Enter the value of r : 5
Area : 78.500000