Question

If 87.5% of atoms of a radioactive element decay in 6 days, then the fraction of atoms of the element that decay in 8 days is

• A. \( \frac{1}{8} \)
• B. \( \frac{7}{8} \)
• C. \( \frac{1}{16} \)
• D. \( \frac{15}{16} \)

Hint:

Memorize the common fractions for half-life decay: - 1 half-life: 1/2 remaining (50% decayed) - 2 half-lives: 1/4 remaining (75% decayed) - 3 half-lives: 1/8 remaining (87.5% decayed) - 4 half-lives: 1/16 remaining (93.75% decayed) Recognizing 87.5% as 7/8 decayed (or 1/8 remaining) instantly tells you that 3 half-lives have passed.

Answer 1

The Correct Option is D