1 world population is doubling in about every 30 years what

1. world population is doubling in about every 30 years. what is the annual % growth rate? What is the exponential growth factor?

2. Assuming 2% of the world\'s coal reserves have been utilized, how many doubling periods will it take for a 40% depletion of this natural resource?

3. The overal efficiency of an old steam power plant with an efficiency of 25% has been improved by adding a topper with an efficiency of 10% and a tailer with an efficiency of 4%. What is the new value for the overall efficiency

Solution

1. Annual growth rate is 2.4% (i.e. 72/30). (Explanation: the Rule of 70 can be used to approximate the doubling time of a population that is growing at a fixed rate of growth) .

   Exponential growth factor is 1.024 (1 + 2.4%)

2. 19 doubling periods it will take for a 40% depletion of this natural resource.(Explanation: 40-2/2)

3. The new value for the overall efficiency will be 28.5%. (Explanation: 25% + 10% of 25% + 4% of 25% = 28.5%)