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# Question 5. Find the sum of first 15 terms of each of the following sequences having nth term as(iii) xn = 6 – n

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This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6

In this question we have been given an arithmetic progression having nth term as xn = 6 – n

And we have to find its sum of first 15 terms.

CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 5(iii)

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1. Given A.P. has nth term, an = 6 – n

and number of terms(n) = 15

So, an = 6 – n = -9

On putting n = 1, we get a, first term of the A.P.,

a = 6 – 1 = 5

S15 = n[a + an]/2

= 15(5 – 9)/2 = 15 x (-2) = -30

Hence, the sum of the first 15 terms of given A.P. is -30.

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