Question

Consider that the half-life of Polonium-210 is 140 days.What approximate daily percentage of decay does Polonium-210 demonstrate?% (Round to two decimals.)(Hint: use the Rule of 70 backwards by dividing by the half-life period instead of the rate.) What percentage of the original amount of Polonium-210 would be left after 425 days of decay? % (Round to two decimals.)
Steve
the fraction left after d days is
0.5^(d/140)
So, after 1 day, that is 0.99506 for a daily decay rate of 0.494%

Now just plug in d=425