Question

Calculate the percentage of the original sample of the radioactive element remains after 24 days. If half life of the radioactive element is 6 days.

• A. 100%
• B. 50%
• C. 25%
• D. 12.5%
• E. 6.25%

Answer 1

Answer: (E)

6.25%

Given : $t_{1/2}=6$ days $t=24$ days

$\therefore$ $n=\frac{t}{t_{1/2}}=\frac{24}{6}=4$

Amount of remaining radioactive element, $R=\frac{R_o}{2^n}$ where $n=\frac{t}{t_{1/2}}=4$

$\therefore$ $\frac{R}{R_o}=\frac{1}{2^4}=0.0625$

$⟹$ Percentage of original sample remained, $\frac{R}{R_o}\times 100=6.25$%