This is an arithmetic progression based question from Chapter name- Arithmetic Progression

Chapter number- 9

Exercise – 9.6

In this question we have been given the arithmetic progression. Also we have to find the sum of its first 13 terms.

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Understanding CBSE Mathematics

Class :- 10th

Question no 11(ii)

Given A.P. has first term(a) = -6,

Common difference(d) = 0 − (−6) = 6

and number of terms(n) = 13.

We know sum of n terms of an A.P. is given by, S

_{n}= n[2a + (n − 1)d] / 2.S

_{13}= 13[2(−6) + (13 − 1)6]/2= 13[(−12) + 72]/2

= 13[30] = 390

Hence, the sum of first 13 terms of the given A.P. is 390.