lem #$9$: The below semilog graph shows an exponentially decreasing quantity $Q(t).$

$$

$($a$)$ What value of $t$ represents the half$-$life of $Q(t)?$

$($b$)$ When does $Q(t)$ reach $90\%$ of its original amount?

$($A$)t$~~$0\mathrm{.}01$

$($B$)t$~~$2\mathrm{.}31$

$($C$)t$~~$0\mathrm{.}50$

$($D$)t$~~$0\mathrm{.}25$

$(E)t$~~$3\mathrm{.}54$

$(F)t$~~$1\mathrm{.}04$

$(G)t$~~$0\mathrm{.}75$

$(H)t$~~$0\mathrm{.}31$

Problem #$9($a$)$: $$ uarr Part $($a$)$ choices.

$($A$)t$~~$1\mathrm{.}34$

$(B)t$~~$0\mathrm{.}97$

$($C$)t$~~$1\mathrm{.}75$

$($D$)t$~~$0\mathrm{.}33$

$(E)t$~~$0\mathrm{.}54$

$(F)t$~~$2\mathrm{.}06$

$(G)t$~~$0\mathrm{.}16$

$(H)t$~~$0\mathrm{.}02$