superman has been disabled by a nearby amount of kryptonite, which decays exponentially. If Superman cannot regain his power until 90% og the kryptonite disintegrates, then how long will it be before he regain his powers?
Use r=-0.138629. Round to the nearest day.
a. 4days c 11days
b 6days d 17days e 21days
Q(t) = Qe^(rt)
The Attempt at a Solution
i tried 0.9Q=Qe^(-0.138629t)
and i was not able to find the answer