Question

1)A particular pain relieving medicine has a decay rate of 10 % per hour. A patient was given a dose of the medicine 7 hours ago and there is currently 68 milligrams of the medicine in the patients bloodstream.

2)How long will the patient need to wait for there to be less than 25 % of the original dose of the medicine left in their bloodstream? Express your answer as a decimal to the nearest tenth of an hour.

Answer 1

.25 > (1 - .10)^(t + 7)

log(.25) > (t + 7) log(.9)