JEE Main 2016 — Sequences And Series Question with Solution
From: JEE Main 2016 (Online) 10th April Morning Slot
Question
Let a1, a2, a3, . . . . . . . , an, . . . . . be in A.P.
If a3 + a7 + a11 + a15 = 72,
then the sum of its first 17 terms is equal to :
If a3 + a7 + a11 + a15 = 72,
then the sum of its first 17 terms is equal to :
Choose an option
Show full solutionCorrect option: A
Correct answer
A306
Step-by-step explanation
As a1 a2 . . . . . an . . . . . are in A.P.
a3 + a15 = a7 + a11 = a1 + a17
Given,
a3 + a7 + a11 + a15 + a15 = 72
(a3 + a15) + (a7 + a11) = 72
2(a1 + a17) = 72
(a1 + a17) = 36
Sum of first 17 terms
= (a1 + a17)
= 36
= 306
a3 + a15 = a7 + a11 = a1 + a17
Given,
a3 + a7 + a11 + a15 + a15 = 72
(a3 + a15) + (a7 + a11) = 72
2(a1 + a17) = 72
(a1 + a17) = 36
Sum of first 17 terms
= (a1 + a17)
= 36
= 306
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