Use the equation y=ae^k^t[/tex], where a represents the initial amount, t represents time and k is the rate of growth or decay. After 12 hours, half of a 16-gram sample of a radioactive element remains.

Question 1
Find the constant k for this element. (4 places)
Write the equation for modeling this element.
If 2 grams of the sample remains, how much time has passed? (nearest whole number)

Question 2
After 22 hours, 25% of a sample of a random element remains. Find the constant k for this element- and write the equation for modeling it's exponential decay.

k = (4 places)

equation
How many samples would remain after 25 hours? (1 place, use a percentage. ex. 16.4%)