This is the Important question based on Arithmetic progression Chapter of R.S Aggarwal book for ICSE & CBSE Board.
Here you have to find the sum of first nth terms.
Question Number 2 of Exercise 11 C of RS Aggarwal Solution
Deepak BoraNewbie
Find the sum of first 26 terms of the AP 1, 3, 5, 7,…..
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Given Ap 1,3,5,7….
a=1
d= 3-1 = 2
n = 26
Sn=n/2[2a+(n-1)d]
S26= n/2[2a+ (n-1)d]
= 26/2 [2 ×1 +(26-1) 2]
= 13[2+(25)2]
= 13 (2 + 50)
= 13×52
= 676
Therefore S26= 676