Radioactive iodine is used to determine the health of thyroid gland. It decays according to the equation
y = ae−0.0856t
, where t is in days. Find the one-fourth life of this substance. Round to the nearest integer.
a. 2 c. 16
b. 7 d. 69

Question

Radioactive iodine is used to determine the health of thyroid gland. It decays according to the equation 
y = ae−0.0856t
, where t is in days. Find the one-fourth life of this substance. Round to the nearest integer.
a. 2 c. 16
b. 7 d. 69

anonymous · Answer

sorry, the equation is $$y=ae ^{-0.0856t}$$

campbell_st · Answer

so in  this question the key is that you need to find the 1/4 life... so 

a = 1  and y = 0.25

so the equation becomes

$$0.25 = 1 \times e^{-0.0856t}$$

so take the log of both sides

ln(0.25) = -0.0856t

now solve for t

hope it helps

anonymous · Answer

@cambell_st thank you, you just saved my day :)