1+2+3+4+5= 15 1+2+3+4+5+.+1856=? can you calculate it in few seconds?

sum of a arithmetic sequence when we have the first and last term

(1856 / 2) x (1 + 1856 ) = 1723926        

(1 is the first term, 1856 is the last term)

1723926 is the answer to this problem. Using  n*(n+1)/2 formula where n= 1856.

Can be solve using arithmetic sum: 

ARITHMETIC SUM = n ( a1 + an)/ 2 

                          = 1856( 1 + 1856) / 2

                          = 1723296

I agree with 

Aneesa Rahman Answer

IT IS A ARITHMETIC SERIES AND THE FORMULA FOR FINDING THE SUM OF ARITHMETIC SERIES IS:-

SUM = (N*(A+L))/2     WHERE N - NUMBER OF TERMS IN THE SERIES

                                            A - FIRST TERM IN THE SERIES

                                            L - LAST TERM IN THE SERIES

THEREFORE,

SUM = (*(1 ))/2

        =  

sum of aritmethic sequence the first terme is 1 and the laste one is 1856

n(n+1)/2

1856*(1856+1)/2=1723296

4 sec

1871

I suppose . means zero

sum of arithmetic sequence ( 1 is the first therm and 1856 is the last)

1+2+3+4+......+1856 = [1856 * ( 1856+1)]/2 = 1723296

The formula to use for this is as follows where y equals the last number                      1856*(1856+1)/2=1723296