Sum of n terms of A.P

Asked by ravikiran | 11th Jul, 2009, 11:42: AM

Expert Answer:

s40={41,42,....80}

so sum of all terms in s40

=41+42+..+80

this is the sum of an A.P.

 with 41 as the first term(a) and 1 as the common diff.(d) and there are total 40 terms(n)

so using the formula

sum of n terms

=n/2[a+l} where l is the last term

we get

reqd sum

=40/2[41+80]

=4840

Answered by  | 11th Jul, 2009, 03:49: PM

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