The amount of radium-224 in a sample was measured at the indicated times... time in days | 0 1 2 3 4 5 6 7 mg | 100 82.7 68.3 56.5 46.7 38.6 31.9 26.4 (just to clarify, 0 corresponds to 100, 1 corresponds to 82.7, ect.. sorry for the messy table above) **A)** estimate how much radium will be left after 10 days Im not sure how to approach this, i know i have to find an equation and plug in 10, but i just don't know the steps to take to find the equation, i looked at the back of my textbook and the equation i was supposed to find is y = e^(4.6051 - .1903t) can someone help me understand the steps that i need to take to get to this equation? **B)** If the sample is considered to be safe when the amount of radium is less than .01mg, estimate how long the sample needs to be stored before it can be safely disposed im completely confused on this one, i have no idea how to approach this.. any help will be appreciated..

You will not be able to do any of those questions without the equation. Here is a starting point. You have an exponential function: So your equation should look like $y=Ae^{bt}$ where A represents the initial amount (at $t=0$) and b could be found using another order pair.