Please solve and show step by step Thanks A 15 g sample of r

A 15 g sample of radioactive iodine decays in such a way that the mass remaining after t days is given by m(t) = 15e^-0.087t, where m(t) is measured in grams. After how ninny days are there only 5 g remaining?

Solution

solution:

m(t)=15e^-0.087t

m(t)=15 at t=0

now finding t when m(t)=5

5=15e^-0.087t

1/3=e^-0.087t

taking log both sides

ln(1/3)=-0.087t

-1.098612=-0.087t

on solving

t=12.62 days