Please find the sum.

Asked by sunil_0010 | 1st Jul, 2009, 10:32: PM

Expert Answer:

we see that the first term=a=54

common diff =d=-3

let the sum of n terms is 513

so using the formula we get,


putting the values of a and d,we get a quadraticc equation, on factorising that

 we get,






so if the number of terms is 18 or 19, we get the sum as zero.

now, for the double answer

since the 18th term




since the common diff is -3,

the next term i.e.the 19th term will be


so whethter you take the sum of 18 terms or 19 terms , it will still be 513

as the 19th term is zero.


Answered by  | 2nd Jul, 2009, 09:37: AM

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