${ }^{210}\mathrm{Bi}$ undergoes $\beta^{-}$ decay to 1/8 of its initial amount in 15 days. The time required for its decay to 1/4 of its initial amount is ____ days (up to two decimal places)
Answer
Answer (as printed): 10.00
The options are missing from the source scan for this question, so there is nothing here for this letter to point at. The letter is what the book printed.
Explanation
Answer: 10.00 days — 1/8 remaining = 3 half-lives in 15 days, so t½ = 5 days. 1/4 remaining = 2 half-lives = 10.00 days.