Question

The amount of radioactive uranium changes with time. The table below shows the amount of radioactive uranium f(t) left after time t:
(pic in comments)
Which exponential function best represents the relationship between f(t) and t?
f(t) = 100(0.25)t
f(t) = 0.25(100)t
f(t) = 100 (0.5)t
f(t) = 0.25(50)t