C program to find sum of n natural numbers without using loops

Here we will learn a C program to find sum of n natural numbers without using loops. First we will read a number from user and store it in variable 'n'. Then we use the simple formula to find the sum of n natural numbers.

C program to find sum of n natural numbers without using loops

The formula is :-

sum=n(n+1)/2

Example 

 Input:

 Enter value of N: 5 

 Logic/formula: 

 sum = N*(N+1)/2 = 5(5+1)/2=5*6/2 = 15 

 Output: sum = 15

 Input:

 Enter value of N: 10

 Logic/formula:

 sum = N*(N+1)/2 = 10(10+1)/2 =10*11/2 = 55 

 Output: sum = 55

Algorithm:-

1. Start 
2. Read n
3. Apply formula 
4. Print the result 
5. Stop.

Learn C program to find sum of n natural numbers using for loop.

Program:-

Here in the program first we input the number n (that is the number upto which we need to find the sum of the natural numbers), then we apply the formula sum=n*(n+1) /2

and display the result

#include <stdio.h>

int main()
{
    int n, sum;
    printf("Enter n: ");
    scanf("%d", &n);
    sum=n*(n+1)/2;
    printf("Sum = %d", sum);

    return 0;

}

Output:-

Enter n: 5                                                                                                      

Sum = 15   

Enter n: 10                                                                                                           

Sum = 55