The half-life of a radioactive isotope is $4 \ hours$. If the initial mass of the isotope is $200 \ g$,then what will be the disintegrated amount of it after $16 \ hours$?

What is the value of the decay constant of a compound having a half-life time $T_{1/2} = 2.95 \text{ days}$?

After $2 \, \text{hours}$,the amount of a certain radioactive substance reduces to $1/16^{th}$ of the original amount (the decay process follows first-order kinetics). The half-life of the radioactive substance is $...... \, \text{min}$.

The half-life of ${}^{65}Zn$ is $245 \ days$. After $x$ days, $75\%$ of original activity remained. The value of $x$ in days is . . . . . . . (Nearest integer)
(Given $: \log 3=0.4771$ and $\log 2=0.3010$ )

For $Ra^{226}$,the $t_{1/2}$ is $1620 \ years$. From $0.001 \ g$ of $Ra$,how many $\alpha$-particles are released per $min$?

Radioactive lead $_{82}Pb^{201}$ has a half-life of $8 \ hours$. Starting from $1 \ mg$ of this isotope,how much will remain after $24 \ hours$?