JEE Main 2019 — Sequences And Series Question with Solution
From: JEE Main 2019 (Online) 10th April Evening Slot
Question
Let , b and c be in G.P. with common ratio r, where 0 and 0 < r
. If 3, 7b and 15c are the first three
terms of an A.P., then the 4th term of this A.P. is :
Choose an option
Show full solutionCorrect option: A
Correct answer
A
Step-by-step explanation
a = a, b = ar and c = ar2
3a, 7b, 15c A.P.
14b = 3a + 15c
14(ar) = 3a + 15(ar2)
15r2 – 14r + 3 = 0
Common difference = 7b – 3a
= 7ar – 3a
4th term is
3a, 7b, 15c A.P.
14b = 3a + 15c
14(ar) = 3a + 15(ar2)
15r2 – 14r + 3 = 0
Common difference = 7b – 3a
= 7ar – 3a
4th term is
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This is a previous-year question from JEE Main 2019, 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.