MCQ
Seven chits are numbered $1$ to $7$. Three are drawn one by one with replacement. The probability that the least number on any selected chit is $5$, is
  • A
    $1 - {\left( {\frac{2}{7}} \right)^4}$
  • B
    $4\,{\left( {\frac{2}{7}} \right)^4}$
  • ${\left( {\frac{3}{7}} \right)^3}$
  • D
    None of these

Answer

Correct option: C.
${\left( {\frac{3}{7}} \right)^3}$
c
(c) $P(5\,{\rm{or}}\,6\,{\rm{or}}7)$ in one draw $ = \frac{3}{7}$

$\therefore $ Probability that in each of $3$ draws, the chits bear $5$ or $6$ or $7$

$= {\left( {\frac{3}{7}} \right)^3}.$

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