Q49 / 90 · KVPY 2011 (SB/SX) · Mathematics

Let $f:(2, \infty) \rightarrow N$ be defined by $f(x)=$ the largest prime factor of $[x]$. Then $\int_{2}^{8} f(x) d x$ is equal to -

  • A
    17
  • Correct answer
    B
    22
  • C
    23
  • D
    25

Solution

$\int_{2}^{8} f(x) d x=2+3+2+5+3+7=22$

Hence, the correct answer is option: 'B'.

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