JAMB Physics 2022 Paper

The equation that establishes a relationship between the amount left undecayed,

A, the initial amount, A0, and the number of half-lives that pass in a period of time t looks like this:

$\frac{1}{2^n} \cdot A_0 = A$

$\frac{1}{2^n} \cdot 120 = 15$

$\frac{1}{2^n}$ = $\frac{15}{120}$

$\frac{1}{2^n}$ = $\frac{1}{8}$

$\frac{1}{2^n}$ = $\frac{1}{2^3}$

$2^n = 2^3$

n = 3