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 overall 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 tailor with an efficiency of 4%. What is the new value for the overall efficiency?