Check for valid triangle and calculate perimeter

Last update on September 18 2025 12:32:36 (UTC/GMT +8 hours)

Check for valid triangle and calculate perimeter

Write a C program that reads three floating-point values and checks if it is possible to make a triangle with them. Determine the perimeter of the triangle if the given values are valid.

Pictorial Presentation:

C Code:

#include <stdio.h>
int main() {
    float  x, y, z, P, A; // Declare variables for side lengths and perimeter

    // Prompt user for the side lengths and store in 'x', 'y', and 'z'
    printf("\nInput the first number: "); 
    scanf("%f", &x);
    printf("\nInput the second number: ");
    scanf("%f", &y);
    printf("\nInput the third number: ");
    scanf("%f", &z);

    if(x < (y+z) && y < (x+z) && z < (y+x)) // Check if the sides can form a triangle
     {  
        P = x+y+z; // Calculate perimeter
        printf("\nPerimeter  = %.1f\n", P); // Print perimeter	 
    }
    else
    {
        printf("Not possible to create a triangle..!"); // Print message if it's not possible to form a triangle
    }
    
    return 0;
}

Sample Output:

Input the first number: 25                                             
                                                                       
Input the second number: 15                                            
                                                                       
Input the third number: 35                                             
                                                                       
Perimeter  = 75.0

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to validate a triangle using side lengths and calculate its area using Heron’s formula if valid.
• Write a C program to check if three side lengths form a valid triangle and determine its type (scalene, isosceles, or equilateral).
• Write a C program to compute the perimeter of a triangle and its semi-perimeter for further geometric calculations.
• Write a C program to verify triangle validity using both side lengths and internal angles, then calculate the perimeter if valid.

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