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NDA 2019
Exam
NDA
Year
2019
Subject
Mathematics
Chapter
Sequences and Series

NDA 2019 · Mathematics · Sequences and Series

If 3rd, 8th and 13th terms of a GP are p, q and r respectively,...

If 3rd, 8th and 13th terms of a GP are p,qp, q and rr respectively, then which one of the following is correct?

Options

  1. Aq2=prq^2=p r
  2. Br2=pqr^2=p q
  3. Cpqr=1p q r=1
  4. D2q=p+r2 q=p+r

Correct answer

A. q2=prq^2=p r

Step-by-step solution

T3=AR2=PT8=AR7=qT13=AR12=rhere q2=P.r.i.e. (AR7)2=(AR2)(AR12)\begin{aligned} & T_3=A R^2=P \\ & T_8=A R^7=q \\ & T_{13}=A R^{12}=r \\ & \text{here } q^2=P. r. \\ & \text{i.e. }\left(A R^7\right)^2=\left(A R^2\right)\left(A R^{12}\right)\end{aligned}
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