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Mathematics · 2022 · 2 marks
CBSE 2022 · Region 4 · Set 2 · Q4
If the first term of an A.P. is $\displaystyle 5$, the last term is $\displaystyle 15$ and the sum of first n terms is $\displaystyle 30$ , then find the value of n .
Marking-scheme solution
$\displaystyle \begin{array}{l}a=5, \text { last term } l=15
S_{n}=30 \Rightarrow \frac{n}{2}(a+l)=30
\Rightarrow \frac{n}{2}(5+15)=30 \Rightarrow n=3\end{array}$
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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.