You can use this exponential decay model calculator to determine the rate of decay for any given substance.
I think the new version of the latest version is a bit problematic because it did not answer even two times in two, it's not like most apps that are scams or a pay to use. Integration, differentiation) have to be included, its quick and easy to use I highly recommend.
Spread the word of this app to more kids. Thisnapp is perfect for everyone in school. Good Really Good, i have been using this app for quite some time now and i think it is a good app and every student is to use it. It's like copying answers from a friend that also shows how to do it and is your phone.
It is far superior to Photo Math. Once that becomes a feature, then it will be the perfect math app, the way it breaks down the solution into steps, make it so helpful for when I find myself with a similar problem and I can apply those steps to solve it.