algebra
posted by Tristan .
Consider that the halflife of Polonium210 is 140 days.What approximate daily percentage of decay does Polonium210 demonstrate?% (Round to two decimals.)(Hint: use the Rule of 70 backwards by dividing by the halflife period instead of the rate.) What percentage of the original amount of Polonium210 would be left after 425 days of decay? % (Round to two decimals.)

algebra 
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
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