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The anwser is Native Americans
By today's standards this period in the US wasn't very democratic, since minorities and women and poor people could not vote. It became less equal because of wealth disparities.
Answer: European countries wanted to settle conflicting claims in Africa.
The decay equation is of the form

where
m(t) = the mass remaining after t minutes
m₀ = the initial mass
k = constant
Because the half-life is 3 minutes, therefore

Therefore
-3k = ln(0.5)
k = ln(0.5)/(-3) = 0.231
Because m₀ = 16 mg, the time, t, for the mass to decay to 1.0 mg is given by

Answer: 22 min (nearest integer)