The half - life of a radioisotope is four hours. If the initial mass of the isotope was $200 \mathrm{~g}$,…

The half - life of a radioisotope is four hours. If the initial mass of the isotope was $200 \mathrm{~g}$, the mass remaining after 24 hours undecayed is
  1. $1.042 \mathrm{~g}$
  2. $4.167 \mathrm{~g}$
  3. $3.125 \mathrm{~g}$
  4. $2.084 \mathrm{~g}$

Solution

$2^6=\frac{200}{a-x}$ $(a-x)=3.125 \mathrm{gm}$

Asked in: JEE Main 2004

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