Write a c program to find out the sum of given A.P.

Definition of arithmetic progression (A.P.):

A series of numbers in which difference of any two consecutive numbers is always a same number that is constant. This constant is called as common difference.

Example of A.P. series:

5 10 15 20 25 …
Here common difference is 5 since difference of any two consecutive numbers for example 20 – 15 or 25 -20 is 5.

Sum of A.P. series:

Sn = n/2(2a + (n-1) d)

Tn term of A.P. series:

Tn = a + (n-1) d 

C Program

#include<stdio.h>
#include<math.h>
int main() {
	int a,d,n,i,tn;
	int sum=0;
	printf("Enter the first number of the A.P. series: ");
	scanf("%d",&a);
	printf("Enter the total numbers in the A.P. series: ");
	scanf("%d",&n);
	printf("Enter the common difference of A.P. series: ");
	scanf("%d",&d);
	sum = ( n * ( 2 * a + ( n -1 ) * d ) )/ 2;
	tn = a + (n-1) * d;
	printf("Sum of the series A.P.: ");
	for (i=a;i<=tn; i= i + d ) {
		if (i != tn)
		             printf("%d + ",i); else
		             printf("%d = %d ",i,sum);
	}
	return 0;
}

Output:

Enter the first number of the A.P. series: 1
Enter the total numbers in the A.P. series: 5
Enter the common difference of A.P. series: 3
Sum of the series: 1 + 4 + 7 + 10 + 13 = 35