Posted by Kristen on Sunday, June 23, 2013 at 12:30pm.
A researchr assistant made 160mg of a radioactive, and found that there was only 20mg left after 45hours.
a) What is the half-life of this substance?
b) Write a function to represent the amount of substance left after x hours
c) If the researcher kew he needed 100mg of the same substance 12 hours after he was able to make a fresh batch, how much should he initially make?
Please help.i have a feeling that something like this will b on my math exam
Please show some steps so I can understand how u get it.
Thanks a bunch I really appreciate it!:)
- math - MathMate, Sunday, June 23, 2013 at 1:30pm
This is an exponential function of the form
Substituting x,y values (20,45)into the equation,
take logs on both sides and solve for k
So the mathematical model becomes:
t=time in hours
y(t)=mass at time t hours.
Half life (value of t when y(t)/y0=1/2)
0.5 = e^(-0.04621t)
Take logs on both sides,
-0.04621t = ln(0.5)
- math - Kristen, Sunday, June 23, 2013 at 1:50pm
can u do a more simpler way...we never learnt log yet..
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