Final answer:
It will take 70 minutes for the activity of bromine-80 to drop from 160 mCi to 10 mCi.
Step-by-step explanation:
To determine how long it will take for the activity of bromine-80 to drop from 160 mCi to 10 mCi, we need to calculate the number of half-lives required. The activity of a radioactive isotope decreases by half in each half-life. So, to determine the number of half-lives, we can divide the initial activity (160 mCi) by the final activity (10 mCi):
Number of Half-Lives = log2(Initial Activity/Final Activity) = log2(160/10) = log2(16) = 4
Since each half-life is 17.6 minutes, we can calculate the total time it will take for 4 half-lives:
Total Time = Number of Half-Lives x Half-Life Time = 4 x 17.6 = 70 minutes