$2(3\mathrm{.}1\mathrm{.}6)$

Initially $100$ milligrams $of$ a radioactive substance was present

$in$ a mineral sample. After $6$ hours the mass had decreased $by$

$3\%.If$ the rate $of$ decay $is$ proportional $to$ the amount $of$ the

substance present $at$ time $t,$ find the amount remaining after $24$

hours.

For $3\mathrm{.}1\mathrm{.}15$ and $3\mathrm{.}1\mathrm{.}16,$ assume Newton's Law $of$ Cooling:

$\frac{dT}{dt}=k(T-T_m)$

where $T_{m}is$ the ambient temperature