An innovative rural public health program is reducing infant mortality in a certain West African country. Pretend the program in Senegal has been reducing infant mortality at a rate 8.7% per year. How long will it take for infant mortality to be reduced by 40%?

Answer 1

100 - 8.7 = 91.3
so every year multiply by .913
.913^n = 0.60

n log .913 == log 0.60
n = log .6/log .913
about 5.6 years