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Sequences and Series — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsSequences and Series1 Mark
MCQ
If $a=3$ and $r=2$ then find the sum up $5^{th}$ term.
  • A
    $95$
  • B
    $82$
  • ✓
    $93$
  • D
    $97$
✓

Answer

Correct option: C.
$93$
We know, $\text{s}_\text{n}=a\frac{\text({r^\text{n}-1)}}{\text({r}-1)}$
Here $a = 3, r = 2$ and $n = 5$
$\text{s}_5=3\frac{(2^5-1)}{(2-1)}$
$=3(32-1)$
$=3\times31$
$=93.$

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