The decay of 942 mg of an isotope is described by the function A(t)= 942e^(0.012t), where t is time in years. Find the amount left after 71 years. Round your answer to the nearest mg. Show all of your work for full credit.

Question

campbell_st · Answer

well the model has been provided.... but my concern is that this is a growth model... so you will have more of the isotope after 71 years than you started with. 

can you check that the power of e isn't negative

$$A(t) = 942e^{-0.012t}$$

but basically all you do to find what is remaining is substitute t = 71 and evaluate

anonymous · Answer

Yeah it is supposed to be negative sorry. So for e^-0.012t I got -0.852 and then would I get the solution by just multiplying that by 942?

campbell_st · Answer

well you have 

$$A(71) = 942 \times e^{-0.012 \times 71}$$

just check your calculation

anonymous · Answer

should it be 942 x 0.42656095634 (rounded to 0.426)?

campbell_st · Answer

yep... that looks fine

anonymous · Answer

Alright, I should be fine from there. Thank you!