Q1 / 118 · NTA Abhyas (JEE Main) 2020 · Mathematics · Sequences and Series

Let an=16,4,1,…… be a geometric sequence. The value of ∑n=1∞Pnn, where Pn is the product of the first n terms, is equal to.

  • A
    8
  • B
    16
  • Correct answer
    C
    32
  • D
    64

Solution

For the G.P. a,ar,ar2,………
Pn=aarar2…..arn-1
=anrnn-12
⇒Pnn=arn-12
⇒∑n=1∞Pnn=a1+r+r+rr+.……
=a1-r
Given, a=16 and r=14
=161-14=32

Hence, the correct answer is option: 'C'.

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