Exactly 1/16 of a given amount of protactinium-234 remains after 26.76 hours. What is the half life of protactinium-234?

This is a problem involving half-lives. We can solve this problem by using the equation as shown: A=Aoe^ - (ln2/t) T where A is the final amount (1gram * assumed), Ao is the initial amount (16g * assumed), t is the half-life * required) and lastly T time elapsed (26.76h). Plug in the values in the equation and you should get 6.69 hours.