Q10 of 47 Page 1

How many terms of the A.P. 27, 24, 21,… should be taken so that their sum is zero?

Let the number of terms in the given A.P. be n; first term, a = 27; common difference, d = 24 – 27 = -3

Sum of n terms, Sn = 0





n(57 – 3n) = 0


∴ n = 0 or n = 13


But we know that number of terms cannot be zero.


Thus, number of terms, n = 19


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