JEE Main 2017 — Sequences And Series Question with Solution
From: JEE Main 2017 (Online) 8th April Morning Slot
Question
If the sum of the first n terms of the series is then n equals :
Choose an option
Show full solutionCorrect option: B
Correct answer
B15
Step-by-step explanation
Given,
+ + + + . . . . . .+ n terms
= + + + + . . . . . .+ n terms
= + 5 + 9 + 13 + . . . . . .+ n terms
= [ 1 + 5 + 9 + 13 + . . . . .+ n terms]
=
=
=
= [n (2n 1)]
According to question,
[n (2n 1)] = 435
2n2 n = 435
n = =
n = = 15 or = 14.5
n = 15 (as n can't be ve)
+ + + + . . . . . .+ n terms
= + + + + . . . . . .+ n terms
= + 5 + 9 + 13 + . . . . . .+ n terms
= [ 1 + 5 + 9 + 13 + . . . . .+ n terms]
=
=
=
= [n (2n 1)]
According to question,
[n (2n 1)] = 435
2n2 n = 435
n = =
n = = 15 or = 14.5
n = 15 (as n can't be ve)
Practice this on the real CBT interface
Solve this JEE Main question (and the rest of the Sequences And Series chapter) on PrepSharp's TCS iON-style CBT player — with timer, bookmarks and session analytics.
Solve interactively →About this question
This is a previous-year question from JEE Main 2017, covering the Sequences And Series chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.