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

एक समांतर श्रेढ़ी में, यदि \(S_{40}=1030 \text { और } S_{12}=57 \text {, तो } S_{30}-S_{10}\) = __________

  1. A 525
  2. B 510
  3. C 515
  4. D 505
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Answer & Solution

Correct Answer

(C) 515

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Detailed explanation

\(\begin{aligned} & S_{40}=1030 \Rightarrow \frac{40}{2}[2 a+39 d]=1030 \\ & \Rightarrow \quad 2 a+39 d=\frac{103}{2}....(1) \\ & \quad S_{12}=57 \Rightarrow \frac{12}{2}[2 a+11 d]=57 \\ & \Rightarrow \quad 2 a+11 d=\frac{57}{6}...(2) \end{aligned}\) समीकरण (1) - समीकरण (2)…
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