A sample of radioactive element has a mass of $10\, gm$ at an instant $t = 0$.The approximate mass of this element in the sample after two mean lives is ..........$gm$

  • [AIPMT 2003]
  • A

    $2.50 $

  • B

    $3.70$

  • C

    $6.30 $

  • D

    $1.35$

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