Question

Expontenial function question please help me! Iodine-131 is a radioactive isotope used in the treatment of thyroid conditions.It has a half-life of 8 days/ hsalf life is the amount of daysfor half of the substance to decay. If a patient is iven 20mgof iondine131 how much of the substance will remain in his body after 32 days?
a.8mg
b.5mg
c.2.5mg
d.1.25mg

Answer 1

Could you help

Answer 2

@zepdrix

Answer 3

@Hero

Answer 4

Please show your work. You were given this problem for a reason. You must have some idea of the required exponential form.

Answer 5

y=20(1-8)^32 is that the right form becayse i think this is expontential decay

Answer 6

I really dont know sometimes my teacher is bad at explaning i dont know how to do it

Answer 7

I don't understand that. Where is the number of days?

\(y = Ce^{-kt}\) -- t is in days

For t = 0, we have C = Initial Population = 20 mg

\(y = (20 mg)e^{-kt}\)

Half-life of 8 days suggests:

\(10 = (20 mg)e^{-k(8)}\) -- The 10 is half of 20.

You can now solve for k and complete the rest of the problem.

Answer 8

we were never taught that

Answer 9

i will try

Answer 10

how do you solve it i am stuck

Answer 11

Use your logarithms.

\(\dfrac{1}{2} = e^{-8k}\)

\(ln(1/2) = -8k\)

Finish up to find k and you are nearly done.