What percentage of a sample original radioactive remains after 5 half-lives?

3.125% If at first there is 100 atoms after 1 half lives there is 100/2=50 atoms after 2 half lives there is 50/2=25 atoms after 3 half lives there is 25/2=12.5 atoms after 4 half lives there is 12.5/2=6.25 atoms after 5 half lives there is 6.25/2=3.125 atoms So there is 3.125% after 5 half lives.

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later

The answer is c. 320 g