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JEE Mains · Maths · STD 11 - 8. sequence and series

જો સમાંતર શ્રેણીનું \(10^{\text {th }}\) મુ પદ \(\frac{1}{20}\) અને તેનું \(20^{\text {th }}\) મુ પદ \(\frac{1}{10},\) હોય તો પ્રથમ  \(200\) પદોનો સરવાળો મેળવો.

  1. A \(50 \frac{1}{4}\)
  2. B \(100 \frac{1}{2}\)
  3. C \(50\)
  4. D \(100\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(100 \frac{1}{2}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{T}_{10}=\frac{1}{20}=\mathrm{a}+9 \mathrm{d}\quad \ldots .(\text {i})\) \(\mathrm{T}_{20}=\frac{1}{10}=\mathrm{a}+19 \mathrm{d} \quad \ldots .(\text {ii})\) \(a=\frac{1}{200}=d\) Hence, \(S_{200}=\frac{200}{2}\left[\frac{2}{200}+\frac{199}{200}\right]=\frac{201}{2}\)
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