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Mathematics · 2022 · 2 marks
CBSE 2022 · Region 2 · Set 3 · Q3
In an A.P. if the sum of third and seventh term is zero, find its $\displaystyle \mathbf{5}^{\text {th }}$ term.Determine the A.P. whose third term is $\displaystyle 5$ and seventh term is 9.
In an A.P. if the sum of third and seventh term is zero, find its $\displaystyle \mathbf{5}^{\text {th }}$ term.
Determine the A.P. whose third term is $\displaystyle 5$ and seventh term is 9.
Marking-scheme solution
\[\Rightarrow a=3, d=1
\]
Therefore A.P. is \(\displaystyle 3,4,5, \ldots\)
5.
Sol
\[\begin{aligned}
& \text { Find the sum of fir } \\
& \mathrm{a}_{\mathrm{n}}=5-2 \mathrm{n} \\
& a_{1}=5-2=3 \\
& a_{20}=5-40=-35 \\
& S_{20}=\frac{20}{2}(3-35)=-320
\end{aligned}
\]
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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.