SOLUTION: I'm having a hard time with exponential functions. Here's the problem: The radioactive bismuth isotope 210Bi has a half-life of 5 days. If there is 100 milligrams of 210Bi prese

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Question 972051: I'm having a hard time with exponential functions. Here's the problem:
The radioactive bismuth isotope 210Bi has a half-life of 5 days. If there is 100 milligrams of 210Bi present at t=0, then the amount f(t) remaining after t days is given by f(t)=100(2)(^-t/5).
a. How much 210Bi remains after 5 days? 10days? 12.5 days?
b. Sketch the graph of f for 0<=t<=30.
Thank you!!

Answer by Boreal(15235)   (Show Source): You can put this solution on YOUR website!
f(5)=100*2^-(5/5)=50 That is just 1 half life and it is 100*2^-1 or 100/2
f(10) is two half-lives, or half of a half. That is 25.
f(12.5) is 100*2^-(2.5)=17.68 mg
y-axis by 10s; x-axis by 1 day

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