1. The problem statement, all variables and given/known data Suppose that you wish to find out how much gasoline is in an underground storage tank. You pour in one gallon of gasoline that contains some half-life radioactive material that causes a Geiger constant to register 48400 counts per minute above background radiation. The next day you remove a gallon from the underground tank and measure its radioactivity to be 100 counts per minute above background 2. Relevant equations none 3. The attempt at a solution The only formula that comes to mind is N=n0e^(kt), so I solved for the decay rate to be .00429 counts/min. But I'm not quite sure how to connect it to the gallons of gasoline.