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Sequences and Series — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsSequences and Series1 Mark
MCQ
Find the sum of first $n$ terms.
  • ✓
    $\frac{\text{n}(\text{n}+1)}{2}$
  • B
    $\Big(\frac{\text{n}(\text{n}+1)}{2}\Big)$
  • C
    $\frac{\text{n}(\text{n}+1)(2\text{n}+1)}{6}$
  • D
    $\Big(\frac{\text{n}(\text{n}+1)}{2}\Big)$
✓

Answer

Correct option: A.
$\frac{\text{n}(\text{n}+1)}{2}$
Sum of first $n$ terms $= 1+2+3+4+……+n$
$\Rightarrow\Big(\frac{\text{n}}{2}\Big)=\text{(a}+\text{b)}$
$=\Big(\frac{\text{n}}{2}\Big)(\text{1}+\text{n})$
$=\frac{\text{n}(\text{n}+1)}{2}.$
 

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