MATH!
posted by Kim .
The mass of a radioactive substance follows an exponential decay model, with a decay rate of 5% per day. A sample of this radioactive substance was taken six days ago. If the sample has a mass of 3 kg today, find the initial mass of the sample. Round your answer to two decimal places.

3 = a(.95)^6
a = 3/.95^6 = 4.08 kg