Q:

C++ Program To Find Sum Of The Following Series 1+2+3+4+5+6 . . . . . n

Logic :-

This is very simple series you just need to print sum of 1 to n terms ,there are two method you can use either use for loop or use formula Running time of using formula is Constant or Running time of using for loop is O(n) in words ' Order of N '

Method 1:- sum of series from 1 to N.

Formula =n(n+1)/2

Method 2:- sum of series from 1 to N.

for(i=1;i<=n;++i)
{
sum+=i;
}

Using Formula

``````#include<iostream>
using namespace std;

int main()
{
int i,n,sum=0;

cout<<"\n1+2+3+4+5+6+……+n\n";
cout<<"\nEnter The Value Of N:\n";
cin>>n;

sum=(n*(n+1))/2;

cout<<"\nSum = "<<sum<<endl;
return 0;
}``````

Output:

1+2+3+4+5.....+n

Enter the value of n:

10

sum=55

Using For Loop

``````#include<iostream>
using namespace std;

int main()
{
int i,n,sum=0;

cout<<"\n1+2+3+4+5+6+……+n\n";
cout<<"\nEnter The Value Of N:\n";
cin>>n;

for(i=1;i<=n;++i)
{
sum+=i;
}
cout<<"\nSum = "<<sum<<endl;
return 0;
}

Method 2:- Using Formula

#include<iostream>
using namespace std;

int main()
{
int i,n,sum=0;

cout<<"\n1+2+3+4+5+6+……+n\n";
cout<<"\nEnter The Value Of N:\n";
cin>>n;

sum=(n*(n+1))/2;

cout<<"\nSum = "<<sum<<endl;
return 0;
}``````

Output:

1+2+3+4+5.....+n

Enter the value of n:

10

sum=55