JEE Main 2020MathematicsSequences and SeriesMediumMCQ

JEE Main 2020 — Sequences and Series Question with Solution

JEE Main 2020 (06 Sep Shift 2)

Question

The common difference of the A.P. b1, b2,....,bm is 2 more than common difference of A.P. a1, a2, ....., an. If a40=-159, a100=-399 and b100=a70, then b1 is equal to :

Choose an option

Show full solutionCorrect option: C
Correct answer
C-81

Step-by-step explanation

Let a1,a1+d1,a1+2d.................first A.P.

a40=a1+39d=-159.....................(1)

a100=a1+99d=-399....................(2)

d=-4,a1=-3

now

b100=a70

⇒b1+99D=a1+69d

b1+99(-2)=-3+69(-4)

(∵Accoding to question D=d+2)

⇒b1=-81

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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.