The radioactivity due to Carbon-14 measured in a piece of a wooden casket from an ancient burial ...

The radioactivity due to Carbon-14 measured in a piece of a wooden casket from an ancient burial site was found to produce 20.0 counts per minute from a given sample,
 
  whereas the same amount of carbon from a piece of living wood produced 160. counts per minute. The half-life of Carbon-14, a beta emitter, is 5730. years. Thus we would estimate the age of the artifact to be about
  A) 14,800 years
  B) 20,000 years
  C) 5,700 years
  D) 17,200 years
  E) 11,500 years

Question 2

Plutonium has a half life of 2.4  104 years. How long does it take for 99 of the plutonium to decay?
 
  A) 1.6  106 y
  B) 1.6  105 y
  C) 1.6  104 y
  D) 1.6  103 y
  E) 1.6  102 y

Question 3

A radioactive substance with a half-life of 3 days has an initial activity of 0.24 Ci. What is its activity after 6 days?
 
  A) 0.48 Ci
  B) 0.02 Ci
  C) 0.06 Ci
  D) 0.23 Ci
  E) 0.12 Ci

Question 4

Which has the greater half-life?
 
  A) Oxygen-19
  B) Cobalt-60
  C) Uranium-238
  D) Strontium-90
  E) Hydrogen-3