$\text { The isotope } { } ^ { 239 } \mathrm { Pu } \text { has a half-life of } 24,100 \text { years. After } 10,000 \text { years, a sample of }$ the isotope is reduced 1.6 grams. What was the initial size of the sample (in grams)? How large was the sample after the first 1,000 years? Round your answers to four decimal places.
A)2.1332 , 2.0727
B)2.7731 , 2.6945
C)1.2799 , 1.2436
D)1.7065 , 1.6582
E)1.0666 , 1.0364

Question

Quizplus · Accepted Answer

The correct answer is A because the half-life of an isotope is the amount of time it takes for half of the isotope to decay. After 10,000 years, half of the sample will have decayed, leaving 1 gram. The initial size of the sample was therefore 2 grams. After the first 1,000 years, one-eighth of the sample will have decayed, leaving 1.875 grams.