JEE Main 2018 — Sequences and Series Question with Solution
JEE Main 2018 (15 Apr Shift 2 Online)
Question
Let and . Then, the least odd natural number , so that , for all is
Choose an option
Show full solutionCorrect option: B
Correct answer
B7
Step-by-step explanation
Which is a G.P. with and number of terms
For least odd natural number , such that
From eqn. (1), we get
As is odd, then
So
Hence, should be 7 .
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This is a previous-year question from JEE Main 2018, 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.