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Mathematics · 2022 · 2 marks
CBSE 2022 · Region 3 · Set 1 · Q2
Find the sum of first $\displaystyle 20$ terms of an AP in which $\displaystyle \mathrm{d}=5$ and $\displaystyle \mathrm{a}_{20}=135$.
Marking-scheme solution
$\displaystyle \begin{array}{l}a+19 \times 5=135 \Rightarrow a=40
S_{20}=\frac{20}{2}[80+19 \times 5]=1750\end{array}$
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CBSE Class 10 Mathematics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.