The problems in this lesson cover natural logarithms. It's importand to understand that the base of a natural logarithm is e, and the value of e is approximately 2.71828. So, to switch 'the natural log of 4 equals 1.39' from logarithmic form to exponential form, the base of the natural log is the base of the power, the number on the other side of the equation is the exponent, and the number inside the natural log is the result. So we have e^1.39 = 4. Going in the other direction, the logarithm definition tells us that to switch e^7 = 1097 from exponential form to logarithmic form, the base of the power is the base of the natural log, the exponent goes on the other side of the equation, and the result goes inside the natural log. So we have 'the natural log of 1097 equals 7.' Students also learn that we use the abbreviation 'ln' to represent natural logs. No natural logarithm calculator is required, and a self-test serves as an interactive natural logarithm worksheet.