JEE Main 2020MathematicsSequences and SeriesEasyMCQ

JEE Main 2020 — Sequences and Series Question with Solution

JEE Main 2020 (05 Sep Shift 2)

Question

If the sum of the first 20 terms of the series log71/2x+log71/3x+log71/4x+…is 460, then x is equal to:

Choose an option

Show full solutionCorrect option: A
Correct answer
A72

Step-by-step explanation

Given log71/2x+log71/3x+log71/4x+…20 times =460
⇒  (2+3+4+…..+21)log7x=460
⇒  202(2+21)log7x=460
⇒  log7x=2
⇒  x=49

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About this question

This is a previous-year question from JEE Main 2020, 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.