1. If theworldspopulation is increasing atannual rate of 1.3% and there were 5 billion people in the year 1986, then in what year will theworldspopulation be 10 billion?

Change in population 10billion 5 billion= 5 billion(double)

Doubling time: 70/1.3% per year= 54 years 1986+54=2040

There is a equation in my energy book for doubling to get percentage growth rate. I don't understand it? or should I have even used this equation of this problem?