4.Two scientists are experimenting with pure samples of isotope X, a highly radioactive substance. The first scientist has a sample with a mass of 20 grams. He measures a half-life of 232 seconds. The second scientist has a sample of the same substance with a mass of 80 grams. What is the half-life that she is most likely to measure?
A. 58 seconds
B. 232 seconds
C. 464 seconds
D. 928 seconds
Wouldn't it be D? Others say B, but I don't get how.
Which of the following is the best definition of half-life for a radioactive substance?
A. Half of the amount of time required for all of the radioactive atoms to decay.
B. The amount of time required for half of the radioactive atoms to decay.
C. The amount of time required for each radioactive atom to decay halfway.
D. All of the above.
It's a play on words, D, right?
5.Radioactive isotopes can be used to find the age of rocks, fossils, or other artifacts. Carbon-14 has a half-life of 5,730 years. Suppose a sample of charcoal from a primitive fire pit contains one eighth of its original amount of carbon-14. How old is the sample?

A. 716 years
B. 17,190 years
C. 22,920 years
D. 45,840 years
B, right?