calculus
posted by brittany .
Pretend the program in Senegal had been reducing infant mortality at a rate
of 12.2 % per year. How long would it take for infant mortality
to be reduced by 31 %?

100  12.2 = 87.8%
dx/dt = .122 x
dx/x = .122 dt
ln x = .122 t + C
x = e^(C.122 t)
x = c e^(.122 t)
when t = 0, x = 100%
so
x = 100 % e^(.122 t)
(100 %31 %) = 100 % e^.122 t
.69 = e^(.122 t)
ln(.69) = .122 t
.371 = .122 t
t = 3.04 years