the half life of cesium 137 is 30 years. Suppose you have a 100 mg sample.?

Question

Find the mass that remains after T years.

Answer 1

Well, you know that it's something * T (-something).

When T = 0, it's 100 mg.

So in mg, it's 100*T^(-C), for some constant C.

You also know that after 30 years it's 1/2 as much as it was after 0 years.

I.e., 30^(-C) = 1/2

Take the logarithm of both sides of that, and from there on it's easy.