gmat1393 wrote:
The half-life of a radioactive element is defined as the amount of time required for the amount of the element to decrease by half. If the half-life of an element is 3 years, how long will it take for the element to be reduced to one-eighth of its original amount?
A. 3 years
B. 9 years
C. 21 years
D. 24 years
E. 27 years
If the amount of the element starts at 1 gram, then after 3 years, it will be at 1/2 gram, then after 6 years it will be at 1/4 gram, and finally, after 9 years, it will be at 1/8 gram.
Answer: B
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67% (01:24) correct 
