Question:C program for area of equilateral triangle 

#include<stdio.h>
#include<math.h>

int main(){

    float a;
    float area;

    printf("Enter size of side of the equilateral triangle : ");
    scanf("%f",&a);

    area = sqrt(3)/4*(a*a);

    printf("Area of equilateral triangle is: %.3f",area);

    return 0;
}
Sample output:
Enter size of side of the equilateral triangle: 5
Area of equilateral triangle is: 10.825

Question:C program for area of right angled triangle 

#include<stdio.h>
int main(){
    float h,w;
    float area;

    printf("Enter height and width of the right angled triangle : ");
    scanf("%f%f",&h,&w);

    area = 0.5 * h * w;
    printf("Area of right angled triangle is: %.3f",area);
    return 0;
}
Sample output:
Enter height and width of the right angled triangle: 10 5
Area of right angled triangle is: 25.000

Question:C program for area of a rectangle 

#include<stdio.h>

int main(){

    float l,w;
    float area;

    printf("Enter size of each sides of the rectangle : ");
    scanf("%f%f",&l,&w);

    area = l * w;
    printf("Area of rectangle is: %.3f",area);

    return 0;
}
[b]Sample output:[b]
Enter size of each sides of the rectangle: 5.2 20
Area of rectangle is: 104.000

Question:C program for area of a trapezium 

#include<stdio.h>

int main(){

    float b1,b2,h;
    float area;

    printf("Enter the size of two bases and height of the trapezium : ");
    scanf("%f%f%f",&b1,&b2,&h);

    area = 0.5 * ( b1 + b2 ) * h ;
    printf("Area of trapezium is: %.3f",area);
    return 0;
}
Sample output:
Enter the size of two bases and height of the trapezium: 5 8 3
Area of trapezium is: 19.500

Question:C program for area of a cube 

#include<stdio.h>

int main(){

    float a;
    float surface_area,volume;

    printf("Enter size of any side of a cube : ");
    scanf("%f",&a);

    surface_area = 6 * (a * a);
    volume = a * a * a;

    printf("Surface area of cube is: %.3f",surface_area);
    printf("\nVolume of cube is : %.3f",volume);

    return 0;
}
Sample output:
Enter size of any side of a cube: 3
Surface area of cube is: 54.000
Volume of cube is: 27.000

Question:C program for area of a cuboids 

#include<stdio.h>
int main(){

    float w,l,h;
    float surface_area,volume,space_diagonal;

    printf("Enter size of width, length and height of a cuboids : ");
    scanf("%f%f%f",&w,&l,&h);

    surface_area = 2*(w*l + l*h + h*w);
    volume = w * l * h;
    space_diagonal = sqrt(w*w + l*l + h*h);

    printf("Surface area of cuboids is: %.3f",surface_area);
    printf("\nVolume of cuboids is : %.3f",volume);
    printf("\nSpace diagonal of cuboids is : %.3f",space_diagonal);

    return 0;
}
Sample output:
Enter size of width, length and height of cuboids: 5 10 4
Surface area of cuboids is: 220.000
Volume of cuboids is: 200.000
Space diagonal of cuboids is: 11.874

Question:C program for area of a cylinder 

#include<stdio.h>
#include<math.h>

int main(){

    float r,h;
    float surface_area,volume;

    printf("Enter size of radius and height of a cylinder : ");
    scanf("%f%f",&r,&h);

    surface_area = 2 * M_PI * r * (r + h);
    volume = M_PI * r * r * h;

    printf("Surface area of cylinder is: %.3f",surface_area);
    printf("\nVolume of cylinder is : %.3f",volume);

    return 0;
}
Sample output:
Enter size of radius and height of a cylinder: 4 10
Surface area of cylinder is: 351.858
Volume of cylinder is: 502.655

Question:Write a c program or code to find or calculate the volume and surface area of cone 

#include<stdio.h>
#include<math.h>

int main(){

    float r,h;
    float surface_area,volume;

    printf("Enter size of radius and height of a cone : ");
    scanf("%f%f",&r,&h);

    surface_area = M_PI * r * (r + sqrt(r*r + h*h));
    volume = (1.0/3) * M_PI * r * r * h;

    printf("Surface area of cone is: %.3f",surface_area);
    printf("\nVolume of cone is : %.3f",volume);

    return 0;
}
Sample output:
Enter size of radius and height of a cone: 3 10
Surface area of cone is: 126.672
Volume of cone is: 94.248

Question:C program for area of a sphere 

#include<stdio.h>
#include<math.h>

int main(){

    float r;
    float surface_area,volume;

    printf("Enter radius of the sphere : ");
    scanf("%f",&r);

    surface_area =  4* M_PI * r * r;
    volume = (4.0/3) * M_PI * r * r * r;

    printf("Surface area of sphere is: %.3f",surface_area);
    printf("\nVolume of sphere is : %.3f",volume);

    return 0;
}
Sample output:
Enter radius of the sphere: 5
Surface area of sphere is: 314.159
Volume of sphere is: 523.599

Question:How to get multiplication of two very large numbers larger or beyond than long int in c programming language 

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#include<string.h>
#define MAX 10000

char * multiply(char [],char[]);
int main(){
    char a[MAX];
    char b[MAX];
    char *c;
    int la,lb;
    int i;
    printf("Enter the first number : ");
    scanf("%s",a);
    printf("Enter the second number : ");
    scanf("%s",b);
    printf("Multiplication of two numbers : ");
    c = multiply(a,b);
    printf("%s",c);
    return 0;
}

char * multiply(char a[],char b[]){
    static char mul[MAX];
    char c[MAX];
    char temp[MAX];
    int la,lb;
    int i,j,k=0,x=0,y;
    long int r=0;
    long sum = 0;
    la=strlen(a)-1;
        lb=strlen(b)-1;
   
        for(i=0;i<=la;i++){
                a[i] = a[i] - 48;
        }

        for(i=0;i<=lb;i++){
                b[i] = b[i] - 48;
        }

    for(i=lb;i>=0;i--){
         r=0;
         for(j=la;j>=0;j--){
             temp[k++] = (b[i]*a[j] + r)%10;
             r = (b[i]*a[j]+r)/10;
         }
         temp[k++] = r;
         x++;
         for(y = 0;y<x;y++){
             temp[k++] = 0;
         }
    }
   
    k=0;
    r=0;
    for(i=0;i<la+lb+2;i++){
         sum =0;
         y=0;
         for(j=1;j<=lb+1;j++){
             if(i <= la+j){
                 sum = sum + temp[y+i];
             }
             y += j + la + 1;
         }
         c[k++] = (sum+r) %10;
         r = (sum+r)/10;
    }
    c[k] = r;
    j=0;
    for(i=k-1;i>=0;i--){
         mul[j++]=c[i] + 48;
    }
    mul[j]='\0';
    return mul;
}
Sample output of above code:
Enter the first number: 55555555
Enter the second number: 3333333333
Multiplication of two numbers:
185185183314814815